ALEC 10-K & 10-Q changes, risk factors and insider trading

We have concentrated a substantial portion of our research and development efforts on the treatment of neurodegenerative diseases, a field that has seen both limited success in drug development and evolving standards for regulatory approval. Further, our product candidates are based on innovative approaches and technologies, making it difficult to predict the time and cost of product candidate development and subsequent regulatory approval.

Our operationsoperations, financial results, and financialthe resultsmarket price of our common stock could be adversely impacted by the effects of worldwide economic conditions, including macroeconomic downturnsdownturns, stemmingglobal fromrecessions, increased inflation, supply chain anddisruptions, trade tariffs or other economicdisruptions impactsin ofglobal trade, pandemics or other public health outbreaksoutbreaks, and geopolitical events and conflicts.

We are highly dependent on our key personnel, and if we are not successful in attracting, motivating, and retaining highly qualified personnel, including as a result of layoffs and furloughs, pausing of recruiting efforts, or regrettable employee attrition, we may not be able to successfully implement our business strategy.

Our existing or future indebtedness and any associated debt covenants onmay impact our business and growth prospects.

We will encounter risks and difficulties frequently experienced by clinical-stage biotechnology companies in rapidly evolving fields, and we have not yet demonstrated an ability to successfully overcome such risks and difficulties. If we do not address these risks and difficulties successfully, our business will suffer.

We have incurred net losses in each year since our inception. We incurred net losses of $119.0 million, $130.4$142.9 million, and $133.3$119.0 millionmillion, for the years ended December 31, 2024, 2023,2025, and 2022,2024, respectively. As of December 31, 2024,2025, we had an accumulated deficit of $829.1$972.1 million.

We have invested significant financial resources in research and development activities, including for our preclinical and clinical product candidates. We do not expect to generate revenue from product sales for several years, if at all. The revenue we have generated from our collaboration arrangements with AbbVieGSK, and GSKpreviously, AbbVie, has been, and from our collaboration arrangement with GSKGSK, is expected to continue to be, variable and limited in amount. For our collaborations with AbbVie and GSK, we have recognized, and for our collaboration with GSK we will continue to recognize, collaboration revenue by measuring the progress towards complete satisfaction of each performance obligation measured as the program costs are incurred. The amount of our future net losses will depend, in part, on the level of our future expenditures and revenue. Moreover, our net losses may fluctuate significantly from quarter to quarter and year to year, such that a period-to-period comparison of our results of operations may not be a good indication of our future performance.

Developing our product candidates is expensive, and we expect to continue to spend substantial amounts as we fund our early-stage research projects and continue to advance our programs through preclinical and clinical development. Even if we are successful in developing our product candidates and obtaining regulatory approvals, launching and commercializing any product candidate will require substantial additional funding.funding as we continue to advance other candidates in our pipeline.

work with our CDMOs to develop and scale up the manufacturing processes for our product candidates or, in the future, establish and operate a manufacturing facility;

attract, hire, and retain qualified personnel provide additional internal infrastructure to support our continued research and development operations and any planned commercialization efforts in the future;

make required payments under the Loan Agreement (defined below);

withstand periods of high rates or sustained periods of inflation; and defend against any product liability claims or other lawsuits related to our products.

addressing impacts on our clinical trials resulting from factors related to the effects of U.S. and worldwide economic conditions, including macroeconomic downturns or global recessions stemming from the economic impacts of increased inflation, supply chain disruptiondisruption, andtrade other economic impacts oftariffs, pandemics or other public health outbreaksoutbreaks, and geopolitical events and conflicts;

maintaining, protecting, expanding, and enforcing our portfolio of intellectual property rights, including patents, trade secrets, and know-how; and attracting, hiring, and retaining qualified personnel in the face of reductions in force, layoffs, hiring freezes, employee attrition, policy changes for foreign worker visas, or a competitive compensation environment.

To date, clinical development of three of our product candidates has been terminated. In November 2024, we decided to stop the long term extension study of our product candidate AL002 based on the results of the INVOKE-2 Phase 2 clinical trial evaluating the safety and efficacy of AL002 in slowing disease progression in individuals with early AD. AL002 failed to meet the primary endpoint in that trial. In January 2025, AbbVie decided to terminate the TREM2 collaboration program, under which AL002 was being developed. AbbVie had previously decided in 2022 to terminate our CD33 collaboration program, after we and AbbVie concluded that further development of AL003, the asset being developed under that program, was not warranted. Additionally, we decided to close the Phase 1 clinical trial for our AL044 product candidate based on initial pharmacokinetics and tolerability data. Because of the numerous risks and uncertainties associated with drug development, we are unable to predict the timing or amount of our expenses, or when we will be able to generate any meaningful revenue or achieve or maintain profitability, if ever. In addition, our expenses could increase beyond our current expectations if we are required by the FDA or foreign regulatory agencies to perform studies in addition to those that we currently anticipate, or if there are any delays in any of our or our current or future collaborators’ clinical trials or the development of any of our product candidates. Even if one or more of our product candidates is approved for commercial sale, we anticipate incurring significant costs associated with launching and commercializing any approved product candidate and ongoing compliance efforts.

Our operations have required substantial amounts of cash since inception,inception. and weWe expect our expenses relating to increaselatozinemab significantlyand AL002 to decrease in the foreseeable future.future as a result of the discontinuation and wind-down of clinical trials for latozinemab and AL002. However, we continue to invest in research and development activities related to programs in our research and preclinical pipeline and to the advancement of those programs into clinical trials. To date, we have financed our operations primarily through the sale of equity securities and upfront payments received in connection with our collaboration arrangements with AbbVieGSK, and GSK.previously, AbbVie. Developing our product candidates and conducting clinical trials for the treatment of neurodegenerative diseases, including FTD, Alzheimer’s disease, and Parkinson’s disease, will require substantial amounts of capital. Even if our clinical trials are successful, preparing for and applying for regulatory approval of our product candidates will require a significant amount of capital, and if we do not have sufficient capital, we may be unable to seek regulatory approval, or regulatory approval may be significantly delayed, in any or all desired markets. Likewise, even if our product candidates are approved, commercialization of our product candidates will require a significant amount of capital, and if we do not have sufficient capital, we may be unable to commercialize our approved products, or commercialization of such products may be significantly delayed, in any or all desired markets.

As of December 31, 2024,2025, we had cash, cash equivalents, and marketable securities of $413.4$256.0 million, which we anticipate provides runway at least through 2026.2027. Our estimate as to how long we expect our existing cash, cash equivalents, and marketable securities to be available to fund our operations is based on assumptions that may prove to be inaccurate, and we could use our available capital resources sooner than we currently expect. In addition, changing circumstances, including periods of rising inflation, may cause us to increase our spending significantly faster than we currently anticipate, and we may need to spend more money than currently expected because of circumstances beyond our control. We may need to raise additional funds sooner than we anticipate if we choose to grow more rapidly than we presently anticipate.

Global markets recently have experienced volatility and instability in connection with macroeconomic downturns stemming from tariffs and global trade uncertainties, increased inflation, supply chain disruption and other economic impacts of pandemics or other public health outbreaks and geopolitical events, including the ongoing conflict between Russia and Ukraine, associated sanctions targeting Russia, and the ongoing conflict in the Middle East, among other matters. In addition, the public market for and stock prices of biotechnology companies have experienced significant downturns over the last few years. Our ability to raise money in the public markets may be severely impacted for the foreseeable future due to these factors. Additional capital may not be available when we need it, on terms acceptable to us, or at all. If adequate capital is not available to us on a timely basis, we may be required to significantly delay, scale back, or discontinue our research and development programs or the commercialization of any product candidates, if approved, or be unable to continue or expand our operations, or otherwise capitalize on our business opportunities, as desired, which could materially affect our business, financial condition, results of operations, and growth prospects and cause the price of our common stock to decline.

Two of ourOur product candidates,candidate, latozinemabnivisnebart and AL101, areis in clinical development, and we continue to develop our research and preclinical pipeline, including our ABC technology platform.platform and ABC-enabled product candidates. Together, the development of these programs and product candidates and this platform requires significant capital investment. Due to the significant resources required, we must focus our programs and product candidates on specific diseases and disease pathways and decide which product candidates to pursue and advance and the amount of resources to allocate to each. One aspect of our drug development strategy is to clinically test and seek regulatory approval for our product candidates in indications in which we believe there is the most evidence that we will be able to quickly generate proof-of-concept data. For certain product candidates, we may choose to expand clinical testing and seek regulatory approvals in other neurodegenerative indications based on genetic and mechanistic overlap with the primary indication.

However, even if our product candidates are able to gain regulatory approval in one indication, there is no guarantee that we will be able to obtain approval in other indications, and we may expend significant resources in seeking such approvals. Our decisions concerning the allocation of research, development, collaboration, management, and financial resources toward particular technology,technologies, product candidates or therapeutic areas may not lead to the development of any viable commercial product and may divert resources away from better opportunities. Similarly, our potential decisions to delay, terminate, or collaborate with third parties in respect of certain programs may subsequently also prove to be suboptimal and could cause us to miss valuable opportunities. If we make incorrect determinations regarding the viability or market potential of any of our programs or product candidates or misread trends in the biopharmaceutical industry, in particular for neurodegenerative diseases, such events could have a material adverse effect on our business, financial condition, and results of operations. As a result, we may fail to capitalize on viable commercial products or profitable market opportunities, be required to forego or delay opportunities with other product candidates or other diseases and disease pathways that may later prove to have greater commercial potential than those we choose to pursue, or relinquish valuable rights to such product candidates through collaboration, licensing, or other royalty arrangements in cases in which it would have been advantageous for us to invest additional resources to retain sole development and commercialization rights. Our reliance on genetic screeninggenetics and use of biomarkers to align patient risk profiles with targeted intervention may eventually require us to develop and use companion diagnostics, which could impact product development costs and timelines depending on the specific diagnostic test and any applicable regulatory requirements that would need to be met to enable its use.

On November 14, 2024, we entered into a loan and security agreement (the Loan Agreement) with our subsidiary, Alector LLC, as a co-borrower, severalthe banks and other financial institutionslenders from time to time party thereto (collectively, the Lenders), and Hercules Capital, Inc. (Hercules), in its capacity as administrative agent and collateral agent for itself and the Lenders, pursuant to which we may access up to two tranches of term loans in an aggregate principal amount of up to $50,000,000 (the Term Loans). The Loan Agreement provides for an initial $25.0 million tranche of Term Loans available through June 30, 2026, $10.0 million of which we borrowed at closing. Our ability to borrow an additional tranche of $25.0 million is subject to agreement on the terms and conditions thereofof the Loan Agreement and at the sole discretion of the Lenders. As security for our obligations under the Loan Agreement, we granted the collateral agent a first priority security interest on substantially all of our assets, subject to certain exceptions. We intend to satisfy our future debt service obligations with our existing cash and cash equivalents. However, we may not have sufficient funds or may be unable to arrange for additional financing to pay the amounts due under our outstanding debt. Funds from external sources may not be available on acceptable terms, if at all.

We are in thePhase clinical stages of development2 for certain product candidates currently in our pipeline.nivisnebart. To date, we have invested substantially in our efforts and financial resources to identify, procure intellectual property for, and develop our programs, product candidates, and ABC technology platform, and provide general and administrative support for these operations. Our future success is dependent on our ability to successfully develop, obtain regulatory approval for, and then successfully commercialize our product candidates, and we may fail to do so for many reasons, including the following:

a product candidate may onupon further study be shown to have harmful side effects or other characteristics that indicate it is unlikely to have an acceptable safety profile or be sufficiently effective or otherwise does not meet applicable regulatory criteria;

We may not be successful in our efforts to further develop our current product candidates. For example, our clinical trials of our product candidates may not demonstrate their safety or efficacy, e.g., the trials may not meet their primary endpoints or otherwise demonstrate evidence of clinical benefit.benefit, or interim analyses of our clinical trials may result in a decision to terminate such trials due to failure of our product candidates to meet certain criteria. We are not permitted to market or promote any of our product candidates before we receive regulatory approval from the FDA or comparable foreign regulatory authorities, and we may never receive such regulatory approval for any of our product candidates. We have product candidates in development, and all will require significant additional clinical development, management of preclinical, clinical, and manufacturing activities, regulatory approval, adequate manufacturing supply, a commercial organization, and significant marketing efforts before we generate any revenue from product sales, if at all.

If any of our product candidates successfully complete clinical trials, we generally plan to seek regulatory approval to market our product candidates in the United States, the European Union, and in additional foreign countries where we believe there is a viable commercial opportunity. We have never commenced, compiled, or submitted an application seeking regulatory approval to market any product candidate.candidate and we may encounter difficulties or delays in doing so, even if such product candidate successfully completed clinical trials. We may never receive regulatory approval, or we may not receive approval in the desired timeframe, to market any product candidates even if such product candidates successfully complete clinical trials, which would adversely affect our viability. To obtain regulatory approval in countries outside the United States, we must comply with numerous and varying regulatory requirements of such countries regarding safety, efficacy, manufacturing and controls, clinical trials, commercial sales, pricing, and distribution of our product candidates. We may also rely on our collaborators or partners to conduct the required activities to support an application for regulatory approval, and to seek approval, for one or more of our product candidates. We cannot be sure that our collaborators or partners will conduct these activities or do so within the timeframe we desire. Even if we (or our collaborators or partners) are successful in obtaining approval in one jurisdiction, we cannot ensure that we will obtain approval in any other jurisdiction. If we are unable to obtain approval for our product candidates in multiple jurisdictions, our business, financial condition, results of operations, and our growth prospects could be negatively affected.

For example, we are developing our proprietary BBB technology platform (Alector Brain Carrier, or ABC) to support selected next-generation product candidates. The goal of our technology is to deliver therapeutic candidates at a lower dose and provide deeper blood-brain barrier penetration while optimizing efficacy, safety and cost. If we are unable to successfully develop and apply our ABC technology as intended, our future pipeline opportunities may be reduced.

We are focusing our research and development efforts on addressing neurodegenerative diseases. Collectively, efforts by biopharmaceutical companies in the field of neurodegenerative diseases have seen limited success in drug development. There are currently limited approved therapeutic options available for patients with FTD, Alzheimer’s disease, Parkinson’s disease, and other neurodegenerative diseases. Recently approved therapies for the treatment of Alzheimer’s disease target a specific pathology (amyloid plaques). Our future success is highly dependent on the successful development of our product candidates for treating neurodegenerative diseases. Developing product candidates and, if approved, commercializing our products for treatment of neurodegenerative diseases subject us to a number of challenges, including obtaining disease modifying activity and efficacious dose in target tissuedosing and obtaining regulatory approval from the FDA and other regulatory authorities who have only a limited set of precedents to rely on.

Our approach to developing treatments for neurodegenerative diseases is based on understanding the complex mechanisms underlying neurodegeneration, including the roles of misfolded proteins, deficient proteins, and lysosomal,dysfunctional immune system,cells and neuronal dysfunction.neurons. Our approach further leverages our understanding of the genetic associations with disease. Through this approach, our product candidates seek to remove toxic proteins, replace critical deficient proteins, and restore immune and nerve cells to normal function. One aspect of this approach is to identify and select targets enriched in microglia and other myeloid immune cells which are genetically associated with neurodegenerative diseases. We identify and develop product candidates, including candidates that utilize our ABC technology, that are designed to cross the blood-brain barrier in sufficient quantity and potency to enable efficacious delivery to the brain and engage the intended target. We seek to identify and develop biomarkers and biomarker assays that can accurately identify signs of a disease or condition, assist us in selecting the right patient population, demonstrate target and pathway engagement, and measure the impact on disease progression of our product candidates. This strategy may not prove to be successful. We cannot be sure that our approach will yield satisfactory therapeutic products that are safe and effective, scalable, or profitable.

inability to generate sufficient preclinical, toxicology, or other in vivo or in vitro data to support the submission of an IND or initiation or continuation of clinical trials;

imposition of delays to clinical trials, including as a result of temporary or permanent clinical hold by regulatory agencies for any number of reasons (see for example our discussions of ARIA inand other risks described in this “Risk Factors” section), including:

the cost of clinical trials of our product candidates being greater than we anticipateanticipate, including costs associated with tariffs or other import or export restrictions;

clinical trials of our product candidates producing negative or inconclusive results, which may result in our deciding, or regulators requiring us, to conduct additional clinical trials or abandon product development programs; and delays in manufacturing, testing, releasing, validating, or importing/exporting sufficient stable quantities of our product candidates for use in clinical trials or the inability to do any of the foregoing.

Any inability to successfully initiate or complete clinical trials could result in additional costs to us or impair our ability to generate revenue. In addition, if we make manufacturing or formulation changes to our product candidates, we may be required to or we may elect to conduct additional studies to bridge our modified product candidates to earlier versions. Clinical trial delays could also shorten any periods during which our products have patent protection and may allow our competitors to bring products to market before we do or sooner than anticipated, which could impair our ability to successfully commercialize our product candidates and may harm our business and results of operations. For example, we had been developing AL002 with AbbVie to treat patients with early Alzheimer’s disease (AD). In November 2024, we announced that AL002 failed to meet the primary endpoint in the INVOKE-2 Phase 2 clinical trial evaluating the safety and efficacy of AL002 in slowing disease progression in individuals with early AD. In January 2025, AbbVie decided to terminate the TREM2 collaboration program, under which AL002 was being developed, which resulted in termination of the AbbVie Agreement. Previously, we had been developing AL003 with AbbVie to treat patients with Alzheimer’s disease but on June 30, 2022, AbbVie provided written notice to us formalizing the decision to terminate the CD33 collaboration program under which AL003 was being developed. GSK, or any other collaboration partner may, in the future decide to terminate collaboration programs based on, among other things, our clinical trial data.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the data safety monitoring board for such trial or by the FDA, EMA, or any other regulatory authority, or if the IRBs of the institutions in which such trials are being conducted suspend or terminate the participation of their clinical investigators and sites subject to their review. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA, EMA, or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions, decreases in regulatory agency funding, staffing, or operations, lack of adequate funding to continue the clinical trial, and impacts of worldwide economic conditions, andincluding othertrade tariffs, public health outbreaks and geopolitical events. Should the FDA or other government agency issue additional guidance that mandates material changes to our clinical trialstrials, e.g., in response to a pandemic or other public health outbreak, the costs of such clinical trials may increase.

We may in the future advance product candidates into clinical trials and terminate such trials prior to their completion, which could adversely affect our business. Further, FDA’s policy to release in “real time” newly issued Complete Response Letters associated with withdrawn or abandoned applications for approval of drug or biological products, if applicable to any of our product candidates, could materially impact our competitive advantage and intellectual property.

The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the trial until its conclusion. We pursued measures to enroll our Phase 3 INFRONT-3 and Phase 2 INVOKE-2 trials, for example, by opening additional clinical trial sites and expanding recruitment efforts to enroll the INFRONT-3 trial. We completed enrollment in those trials in the second half of 2023. However, we may experience difficulties in patient enrollment in other clinical trials for a variety of reasons, including:

We are a late-stage clinicalclinical-stage biotechnology company with a mission to make degenerative brain disorders history. Our robust portfolio ofdeveloping therapies is focused on counteracting the devastating progression offor neurodegenerative diseases, particularlywith ina focus on areas of high unmet needmedical whereneed. therapeuticOur optionswork areis limited.informed Weby areadvances atin thedisease forefront of a scientific and clinical revolution, committed to understanding the complex mechanisms that drive neurodegenerative diseases,biology, including the roles of toxic misfolded proteins,or deficient proteins, lysosomal dysfunction, and lysosomal, immune system, and neuronal dysfunction.pathway disruption.

Our operations have been financed primarily through our collaborationscollaboration with AbbVieGSK, our previous collaboration with AbbVie, entered into in October 2017 and GSKterminated andin February 2025, the issuance and sale of convertible preferred stock and of common stock upon the completion of our initial public offering (IPO), and follow-on equity and debt financings.

To date, we have not had any products approved for sale and have not generated any product or royalty revenue from product sales. Further, we do not expect to generate revenue from product sales until such time, if ever, that we are able to successfully complete the development and obtain marketing approval for one of our product candidates. We will continue to require additional capital to develop our product candidatescandidates, advance our research and preclinical programs, and fund operations for the foreseeable future. We have incurred net losses in each year since inceptioninception, and we expect to continue to incur net losses for the foreseeable future. Our ability to generate product revenue will depend on the successful development and eventual commercialization of one or more of our product candidates. Our net losses were $119.0$142.9 million, $130.4 million,million and $133.3$119.0 million for the years ended December 31, 2024, 2023,2025 and 2022,2024, respectively. As of December 31, 2024,2025, we had an accumulated deficit of $829.1$972.1 million. Substantially all of our net losses have resulted from costs incurred in connection with our research and development programs and from general and administrative costs associated with our operations. We expect our expenses will increase substantially in connection with our ongoing activities, as we:

acquire, discover, validate, and develop additional product candidates;

require the manufacture of suppliesdrug supply for our research, preclinical studies and clinical trials; and obtain, maintain, expand, and protect our intellectual property portfolio.

On NovemberMarch 25,7, 2024,2025, we committed to a plan to reduce our workforce by approximately 17%13% to better align our resources with our strategic priorities.priorities including advancing our preclinical and research pipeline. We initiated such reduction in force impacting approximately 4125 employees across the organization. On October 21, 2025, we initiated a reduce in force that impacted approximately 47% our workforce in order to align resources with the Company’s strategic priorities following the results of the Phase 3 INFRONT-3 clinical trial evaluating the safety and efficacy of latozinemab in individuals with frontotemporal dementia due to a progranulin gene mutation (FTD-GRN). As of December 31, 2024,2025, we had cash, cash equivalents, and marketable securities of $413.4$256.0 million, which we anticipate provides runway at least through 2026.2027.

We have not generated any product or royalty revenue from product sales and do not expect to do so in the near future. Our revenue to date has been primarily related to the AbbVie Agreement and GSK Agreement for the license and co-development of product candidates with those parties. We recognizerecognized revenue from the upfront payments and the milestone payment received from AbbVie over time as services arewere provided. We recognize revenue from the upfront payments from GSK at a point in time for a development license and over time for research and development services. Revenues for research and development services are recognized as the program costs are incurred by measuring actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation.

Under the terms of the GSK Agreement, we received $700 million in upfront payments, of which $500 million was received in August 2021 and $200 million was received in January 2022. In addition, we willmay be eligible to receive up to an additional $1.5 billion in clinical development, regulatory, and commercial launch-related milestone paymentspayments, forsubject latozinemabto successful advancement and AL101.commercialization of product candidates in multiple indications under the agreement. Alector and GSK are jointlyconducting developingdevelopment latozinemab and AL101. In May 2023, we and GSK amended the GSK Agreement.jointly. Under the current terms of the GSK Amendment,Agreement, we are responsible for funding GSK’s and our development costs up to $140.5 million for the conduct of the initial Phase 2 clinical trial of AL101nivisnebart in AD.

In the United States, Alector and GSK willagreed to equally share profits and losses from commercialization of latozinemabproduct andcandidates AL101.under the agreement. We may opt out of the sharing of development costs and of profit and losses from commercialization in the United States on a product-by-product basis. In such case, we will no longer conduct development or commercialization of that product andproduct, we will receive royalties on net sales of the product in the United States instead of a share of profits.profits, and certain milestones will be reduced. Outside of the United States, GSK willagreed beto responsible for commercialization of latozinemab and AL101nivisnebart for all indications, and we will be eligible for double-digit tiered royalties.

We expect that our revenue for the next several years will be derived primarily from the GSK Agreement. The balance of deferred revenue was $195.8$171.2 million as of December 31, 2024,2025, related to the GSK Agreement. The deferred revenue is expected to be recognized over the research and development period of the programs through the completion of the initial Phase 2 clinical trials for specified indications for latozinemab and AL101.nivisnebart.

costs related to production of research, preclinical, and clinical materials, including fees paid to contract manufacturers;

laboratory and vendor expenses related to the execution of research, preclinical studies and clinical trials;

Specific program expenses include expenses associated with the development of our most advanced product candidates:candidate, latozinemab,nivisnebart, which is being studied in a pivotal Phase 3 clinical trial, INFRONT-3; and AL101, which is being studied in athe PROGRESS-AD Phase 2 clinical trial. We also have expenses related to the discoveryresearch and development of future product candidates and separately tracked expenses related to programs that we expect to move out of preclinical studies and into Phase 1 clinical trials. These expenses primarily relate to salaries and benefits, stock-based compensation, facility expenses, including depreciation, and lab consumables.

Where we share costs with our collaboration partners, such as in our GSK Agreement, research and development expenses may include cost sharing reimbursements from, or payments to, our partner.

At this time, we cannot reasonably estimate or know the nature, timing, and estimated costs of the efforts that will be necessary to complete the development of, and obtain regulatory approval for, any of our product candidates. We expect our research and development expenses relating to increaselatozinemab substantiallyand forAL002 to decrease in the foreseeable future as a result of the discontinuation and wind-down of clinical trials for latozinemab and AL002. However, we continue to invest in research and development activities related to developingprograms our product candidates, as our product candidates advance into later stages of development, as we begin to conduct larger clinical trials, as we seek regulatory approvals for any product candidates that successfully complete clinical trials, and incur expenses associated with hiring additional personnel to supportin our research and developmentpreclinical efforts.pipeline Theand processto the advancement of conductingthose theprograms necessaryinto clinical research to obtain regulatory approval is costly and time-consuming, and the successful development of our product candidates is highly uncertain.trials.

The following table sets forth selected consolidated statements of operations data for the fiscal years indicated and the percentage change in such data from year to year. These historical operating results may not be indicative of the results for any future period. A discussion of our results of operations for the comparison of the years ended December 31, 2023 and 2022 can be found on page 103 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2023 filed with the SEC on February 27, 2024.

Collaboration revenue was $21.0 million for the year ended December 31, 2025, compared to $100.6 million for the year ended December 31, 2024,2024. comparedThe todecrease $97.1of $79.6 million forin the year ended December 31, 2023. The increase of $3.5 millionrevenue was mainlyprimarily due to athe $15.9satisfaction millionof increasethe inperformance revenueobligations recognizedassociated forwith the AL002 program and athe $9.8latozinemab millionFTD-C9orf72 increasePhase 2 trial in the fourth quarter of 2024, resulting in lower revenue recognized for the latozinemab programs, offset by a $22.2 million decrease in revenue recognized for the AL101 programs.2025. Revenues are recognized as the program costs are incurred by measuring actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation.

Our primary uses of cash are to fund our operations, which consist primarily of research and development expenditures related to our programs, and to a lesser extent, general and administrative expenditures. We expect our expenses to continue to increase in connection with our ongoing activities, in particular as we continue to advance our product candidates and our discovery and research programs. In addition, we expect to incur additional costs associated with operating as a public company.

As of December 31, 2024,2025, we had cash, cash equivalents, and marketable securities of $413.4$256.0 million, which we anticipate provides runway at least through 2026.2027. We reduced our workforce to better align our resources with our current strategic priorities and maintain our expectations with respect to our ability to fund our operations. We have based this estimate on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we currently expect. We may also choose to seek additional financing opportunistically. We may seek to raise capital through public equity or debt financings, license agreements, collaborative agreements or other arrangements with other companies, asset sales, or through other sources of financing. We have an omnibus shelf registration statement on Form S-3 with the SEC, which became effective on May 1, 2023, which permits us to issue up to $400 million in common stock, other equity securities and/or debt securities. OnWe Novemberwill 7,need 2023,to obtain substantial additional funding in the future for our research and development activities and continuing operations. If we enteredare into an at-the-market sales agreement with TD Cowen pursuantunable to whichraise capital when needed or on favorable terms, we maywould offerbe forced to delay, reduce, or eliminate our research and selldevelopment fromprograms timeor tofuture timecommercialization through TD Cowen up to $125,000,000 of shares of our common stock, in such share amounts as we may specify by notice to TD Cowen. On January 17, 2024, we entered into an underwriting agreement with Cantor, pursuant to which we offered and sold 10,869,566 shares of the Company’s common stock at a price per share of $6.57 paid by Cantor. Additionally, on November 14, 2024, we entered into the Loan Agreement with our subsidiary, Alector LLC, as a co-borrower, the Lenders, and Hercules Capital, Inc., in its capacity as administrative agent and collateral agent for itself and the Lenders, pursuant to which we may access up to two tranches of Term Loans in an aggregate principal amount of up to $50,000,000. The initial tranche of Term Loans provides for an aggregate principal amount of up to $25,000,000 through June 30, 2026, subject to the satisfaction of certain conditions. The second tranche of Term Loans provides for up to $25,000,000 and is available at the sole discretion of the Lenders. We borrowed $10,000,000 principal amount of the initial tranche of Term Loans on the closing date of the Loan Agreement.efforts.

We expectwill need to obtain substantial additional funding in the future for our research and development activities and continuing operations. If we wereare unable to raise capital when needed or on favorable terms, we would be forced to delay, reduce, or eliminate our research and development programs or future commercialization efforts.

ourthe abilitytiming toand maintainprogress of our current research and development programs and our ability to establish new research and development programs;

addition andor retention of key research and development personnel;

our efforts to maintain or enhance operational, financial, and information management systems, and hire additionalor retain personnel, including personnel to support development of our product candidates;

the effects of macroeconomic conditions, including inflationary pressures and economic impacts of tariffs and global trade disruptions; and the costs involved in prosecuting, defending, and enforcing patent claims and other intellectual property claims.

We recognize collaboration revenue at a point in time if control of the promised good or service has been transferred to the customer. We recognize collaboration revenue over time by measuring the progress toward complete satisfaction of the performance obligation using an input measure. In order to recognize revenue over the research and development period, we measure actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation. Revenues are recognized as the program costs are incurred. We re-evaluate the estimate of expected costs to satisfy the performance obligation each reporting period and make adjustments for any significant changes. Clinical trials are expensive and can take many years to complete, and the outcome is inherently uncertain. Changes in our forecasted costs are likely to occur over time based upon changes in clinical trial procedures set forth in protocols, changes in estimates of manufacturing costs, or feedback from regulators on the design or operation of our clinical trials. We have had changes to the overall expected costs to satisfy the performance obligations from period to period. For the year ended December 31, 2024,2025, we recorded an $8.9 million increase to collaboration revenue under the AbbVieGSK Agreement due to changesa decrease in estimatedtotal expected costs to satisfy the performance obligations resulting fromfor the termination of the AL002nivisnebart program.

We may not be successful in our efforts to carry out our obligations under ourany collaborations for our product development and research programs; for instance, without limitation, we may not complete in a timely manner or at all our contractual obligations to GSK.programs.

In October 2025, we decided to stop the open label extension portion of the INFRONT-3 trial and the continuation study of our product candidate latozinemab based on the results of the INFRONT-3 Phase 3 clinical trial evaluating the safety and efficacy of latozinemab in slowing disease progression in individuals with frontotemporal dementia due to a progranulin gene mutation (FTD-GRN). LatozinemabWe failedpreviously toterminated meetdevelopment of our AL002 product candidate based on the results of the INVOKE-2 Phase 2 clinical co-primarytrial, endpointsterminated indevelopment thatof trial.our AL003 product candidate, and closed the Phase 1 clinical trial for our AL044 product candidate.

We have incurred net losses in almost every reporting period since our inception. We incurred net losses of $22.9$23.0 million and $40.5$45.9 million for the three and six months ended MarchJune 31,30, 20262026, respectively. We incurred net losses of $30.5 million and $71.0 million for the three and six months ended June 30, 2025, respectively. As of MarchJune 31,30, 2026, we had an accumulated deficit of $995.0$1,018.0 million.

We have invested significant financial resources in research and development activities, including for our preclinical and clinical product candidates. We do not expect to generate revenue from product sales for several years, if at all. The revenue we have generated from our collaboration arrangements with GSK, and previously, AbbVie, has been, and from our collaboration arrangement with GSK, is expected to continue to be, variable and limited in amount.

Our prior losses and expected future losses have had and will continue to have an adverse effect on our stockholders’ equity (deficit) and working capital. In any particular quarter or quarters, our operating results could be below the expectations of securities analysts or investors, which could cause our stock price to decline.

receiving milestones and other payments under our current and any future collaboration arrangements;

Our operations have required substantial amounts of cash since inception. We expect our expenses relating to latozinemablatozinemab, nivisnebart, and AL002 to decrease in the foreseeable future as a result of the discontinuation and wind-down of clinical trials for latozinemablatozinemab, nivisnebart and AL002. However, we continue to invest in research and development activities related to programs in our research and preclinical pipeline and to the advancement of those programs into clinical trials. To date, we have financed our operations primarily through the sale of equity securities and upfront payments received in connection with our collaboration arrangements with GSK, and previously, AbbVie. Developing our product candidates and conducting clinical trials for the treatment of neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease, will require substantial amounts of capital. Even if our clinical trials are successful, preparing for and applying for regulatory approval of our product candidates will require a significant amount of capital, and if we do not have sufficient capital, we may be unable to seek regulatory approval, or regulatory approval may be significantly delayed, in any or all desired markets. Likewise, even if our product candidates are approved, commercialization of our product candidates will require a significant amount of capital, and if we do not have sufficient capital, we may be unable to commercialize our approved products, or commercialization of such products may be significantly delayed, in any or all desired markets.

As of MarchJune 31,30, 2026, we had cash, cash equivalents, and marketable securities of $206.5$172.8 million, which we anticipate provides runway at least through 2027. Our estimate as to how long we expect our existing cash, cash equivalents, and marketable securities to be available to fund our operations is based on assumptions that may prove to be inaccurate, and we could use our available capital resources sooner than we currently expect. In addition, changing circumstances, including periods of rising inflation, may cause us to increase our spending significantly faster than we currently anticipate, and we may need to spend more money than currently expected because of circumstances beyond our control. We may need to raise additional funds sooner than we anticipate if we choose to grow more than we presently anticipate.

We cannot be certain that any of our product candidates will be successful in any future clinical trials. Our future clinical trials of our product candidates may not demonstrate their safety or efficacy, either in the indications currently being tested or in any other indications, or either as single agent therapies or in combination with other therapeutics. For example, we were developing our product candidate latozinemab with GSK to treat patients with FTD-GRN. Latozinemab was an investigational human monoclonal antibody (mAb) designed to block and internalize the sortilin receptor (SORT1) to elevate PGRN levels in the brain. In October 2025, latozinemab failed to meet the clinical co-primary endpoint in the INFRONT-3 Phase 3 trial, and we decided to stop the open label extension portion of the Phase 3that study and the continuation study of latozinemablatozinemab. basedOn onJuly 6, 2026, GSK provided written notice to the resultsCompany ofterminating the INFRONT-3GSK Phase 3 clinical trial evaluating the safety and efficacy of latozinemab in slowing disease progression. Latozinemab failed to meet the clinical co-primary endpoint in that trial.Agreement.

In November 2024, our AL002 program was terminated based on the results of the INVOKE-2 Phase 2 clinical trial evaluating the safety and efficacy of AL002 in slowing disease progression in individuals with early AD, in which AL002 failed to meet the primary endpoint. In 2022, we and AbbVie concluded that further development of our product candidate AL003 was not warranted. In the future, GSK or any otherOur collaboration partnerwith mayAbbVie decideterminated toin terminate a collaboration program based on, among other things, our clinical trial data.2025.

We may not be successful in our efforts to continue to develop and apply our ABC platform, to create a pipeline of product candidates from our research and drug discovery platform or to develop commercially successful products. If we fail to successfully identify and develop additional product candidates from our research and drug discovery platform, our commercial opportunity may be limited.

ForWe example,have wedeveloped areand developingcontinue to develop our proprietary BBB technology platform (Alector Brain Carrier, or ABC) and have applied it to support selected product candidates.candidates in our research and preclinical pipeline. The goal of our ABC technology is to deliver therapeutic candidates at a lower dose and provide deeper blood-brain barrier penetration while optimizing efficacy, safety and cost. If we are unable to successfully develop and apply our ABC technology does not function as intended, our future pipeline opportunities may be reduced.

We also seek to develop product candidates incorporating our ABC technology in our preclinical and research pipeline for a range of neurodegenerative diseases. For example, we are currently pursuing AL037/AL137, our brain-penetrant anti-amyloid beta antibody program in AD; AL050, our brain-penetrant GCase enzyme replacement therapy, in Parkinson’s disease; and AL164, our brain-penetrant tau siRNA, in AD, all of which are enabled by ABC using a TfR-based transport mechanism. Those product candidates have complex structures and multiple functional elements, relative to standard antibody candidates that have previously been our main focus. Therefore, those product candidates may pose additional challenges, including with respect to their manufacture and their ability to function as intended. If we are unable to advance those programs or other preclinical or research candidates, or if we encounter significant delays in our anticipated timeline for progressing those candidates, our future pipeline opportunities may be reduced.

Our approach to developing treatments for neurodegenerative diseases is based on understanding the complex mechanisms underlying neurodegeneration, including the roles of misfolded proteins, deficient proteins, and dysfunctional immune cells and neurons. Our approach further leverages our understanding of the genetic associations with disease. Through this approach, our product candidates seek to remove toxic proteins, replace critical deficient proteins, and restore immune and nerve cells to normal function. One aspect of this approach ishas been to identify and select targets enriched in microglia and other myeloid immune cells which are genetically associated with neurodegenerative diseases. Another aspect of this approach is to select known or validated targets for neurodegenerative diseases. We identify and develop product candidates, including candidates that utilize our ABC technology,technology thatand are designed to cross the blood-brain barrier in sufficient quantity and potency to enable efficacious delivery to the brain and engage the intended target. We seek to identify and develop biomarkers and biomarker assays that can accurately identify signs of a disease or condition, assist us in selecting the right patient population, demonstrate target and pathway engagement, and measure the impact on disease progression of our product candidates. This strategy may not prove to be successful. We cannot be sure that our approach will yield satisfactory therapeutic products that are safe and effective, scalable, or profitable.

competing clinical trials for similar therapies or targetingthat target patient populations meeting our patient eligibility criteria;

Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure can occur at any time during the clinical trial process. The results of preclinical studies of our product candidates may not be predictive of the results of early-stage or later-stage clinical trials, and results of early-stage clinical trials of our product candidates may not be predictive of the results of later-stage clinical trials. The results of clinical trials in healthy volunteers or in one set of patients or disease indications may not be predictive of those obtained in another. In some instances, there can be significant variability in safety or efficacy results between different clinical trials of the same product candidate due to numerous factors, including changes in trial procedures set forth in protocols, differences in the size and type of the patient populations, changes in and adherence to the dosing regimen and other clinical trial protocol elements, and the rate of dropout among clinical trial participants. Open-label or long-term extension studies may also extend the timing and cost of a clinical program substantially.

Product candidates in later stages of clinical trials may fail to show the desired safety and efficacy profile despite having progressed through preclinical studies and initial clinical trials. A number of companies in the biopharmaceutical industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or unacceptable safety issues, notwithstanding promising results in earlier trials. This is particularly true in neurodegenerative diseases, where failure rates historically have been higher than in many other disease areas. Most product candidates that begin clinical trials are never approved by regulatory authorities for commercialization. For example, in April 2026, we and GSK decided to discontinue the PROGRESS-AD Phase 2 clinical trial of nivisnebart in early AD following thea pre-specified interim futility analysis. An independent data monitoring committee concluded that the trial was unlikely to meet its primary endpoint ofat slowing disease progression attrial completion. In October 2025, because latozinemab did not meet the clinical co-primary endpoint in the INFRONT-3 Phase 3 clinical trial, we decided to stop the open label portion of that trial and the continuation study for latozinemab. In November 2024, we decided to stop the long term extension study of our product candidate AL002 after results from the INVOKE-2 Phase 2 clinical trial showed that AL002 failed to meet the primary endpoint.

There are a number of large pharmaceutical and biotechnology companies that are currently pursuing the development of products for the treatment of neurodegenerative diseases, including Alzheimer’s disease and Parkinsons disease. Many of these current or potential competitors, either alone or with their strategic partners, have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals, and marketing approved products than we do. For example, in July 2024, the FDA approved donanemab, which was developed by Eli Lilly and Company,Company (Eli Lilly), for the treatment of Alzheimer’s disease. Donanemab targets amyloid plaques by binding to insoluble N-truncated pyroglutamate amyloid beta. In January 2023, the FDA granted accelerated approval, and in July 2023, the FDA granted full approvalapproval, to lecanemab, an anti-amyloid beta protofibril antibody for the treatment of Alzheimer’s disease developed by Eisai Co., Ltd. (Eisai) and Biogen Inc. (Biogen). Lecanemab has been approved as a treatment for slowing progression of mild cognitive impairment and mild dementia due to Alzheimer’s disease in Japan, and in April 2025, lecanemab received final marketing authorization in Europe for treating mild cognitive impairment or mild dementia due to Alzheimer’s disease in patients who have only one or no copy of the ApoE4 allele.

There are competing pharmaceutical and biotechnology companies, such as Denali Therapeutics, Inc. (“Denali”), F. Hoffman La Roche Ltd. (“Roche”), Aliada Therapeutics, Inc. (acquired by AbbVie), Eli Lilly, BioArctic, JCR Pharmaceuticals, Korsana, Arrowhead, and Ossianix, who have developed and continue to develop technologies for the transport of products across the blood-brain barrier using transferrin receptor (TfR)-based transfer mechanisms. Other companies may successfully develop technologies for blood-brain barrier transport that are based on mechanisms other than TfR and that effectively compete with TfR-based mechanisms. Our ABC platform, which uses a TfR-based transfer mechanism, faces competition from such third-party technologies.

Additionally, those competing blood-brain barrier transport technologies are being applied to antibodies and product candidates that act on the same disease targets as we are pursuing. For example, Denali, Korsana, and Roche are advancing antibody candidates, botheach of which targettargets A-beta and incorporateincorporates blood-brain barrier transport mechanisms that act through TfR, and Arrowhead is advancing a tau-siRNA candidate with a TfR binding antibody fragment. Other companies, including Bial, Vanqua Bio, Inc., Gain Therapeutics, Inc., Prevail, Spur Therapeutics, Voyager Therapeutics, Inc., Denali, and Roche have clinical or pre-clinical programs targeting GCase through allosteric activation, gene therapy, or enzyme replacement, with the latter approach incorporating TfR-based blood-brain barrier transfer mechanisms. Those and other competitors are pursuing product candidates that act on some of the same targets or through comparable mechanisms of action as we are pursuing.

The processes involved in manufacturing our product candidates are complex, expensive, highly-regulated, and subject to multiple risks. Manufacturing certain product candidates, such as non-antibody protein product candidates or product candidates incorporating ABC and other active components, may be especially challenging and may require complex and integrated supply chains and CDMO networks. Further, as product candidates are developed throughfrom preclinical studies tothrough late-stage clinical trials towards approval and commercialization, it is common that various aspects of the development program, such as manufacturing methods, are altered along the way in an effort to scale processes and optimize results. Such changes carry the risk that they will not achieve these intended objectives, and any of these changes could cause our product candidates to perform differently and affect the results of planned clinical trials or other future clinical trials.

In addition, the manufacturing process for any products that we may develop is subject to FDA, EMA, and other foreign regulatory authority approval processes,processes and continuous oversight, and we will need to contract with manufacturers who can meet all applicable FDA, EMA, and other foreign regulatory authority requirements, including complying with current good manufacturing practices (cGMPs) on an ongoing basis. Further, the manufacturers that we or our collaboration partners work with will be subject to any future legislation by Congress or other government action that may curtail the ability of foreign CDMOs to provide services to U.S. biotechnology companies. In addition, tariffs may be imposed on products that are manufactured by foreign CDMOs and imported into the U.S. to incentivize manufacturing activity in the U.S. versus abroad. If we or our third-party manufacturers are unable to reliably produce products to specifications acceptable to the FDA, EMA, or other regulatory authorities, we may not obtain or maintain the approvals we need to commercialize such products. Even if we obtain regulatory approval for any of our product candidates, there is no assurance that either we or our CDMOs will be able to manufacture the approved product to specifications acceptable to the FDA, EMA, or other regulatory authorities, to produce it in sufficient quantities to meet the requirements for the potential launch of the product, or to meet potential future demand. Any of these challenges could delay completion of clinical trials, require bridging clinical trials or the repetition of one or more clinical trials, increase clinical trial costs, delay approval of our product candidates, impair commercialization efforts, increase our cost of goods, and have an adverse effect on our business, financial condition, results of operations, and growth prospects.

In Europe, the European Commission has granted marketing authorizations for several biosimilar products pursuant to a set of general and product class-specific guidelines for biosimilar approvals issued over the past few years. In Europe, a competitor may reference data supporting approval of an innovative biological product,product but will not be ablesubject to getvarious itlimitations onthat impact the market until 10 years after the time of approval of the innovative product. This 10-year marketing exclusivity period will be extended to 11 years if, during the first eight of those 10 years, the marketing authorization holder obtains an approval for one or more new therapeutic indications that bring significant clinical benefits compared with existing therapies.period. In addition, companies may be developing biosimilar products in other countries that could compete with our products, if approved.

Additionally, reorganization of the U.S. Department of Health and Human Services (HHS) under its current leadership, changes in the current administration’s focus and policies, departure of senior leadership at the FDA and other agencies under HHS, and reductions in agency funding and staffing at HHSHHS, maygovernment impact operations at the FDA as well as other federal agencies. Government shutdown, staff departures at the FDA,shutdowns, lapses in government appropriations, and changes in the staffing and resourcing levels at the FDA may impact the FDA’s operations, including the FDA’s ability to meet current review, approval, and inspection schedules, as well as our ongoing correspondence with the FDA, including correspondence regarding progression to the next phases of development. Likewise, restructuring, downsizing, and decreased funding of federal agencies including the FDA may result in our not realizing all the benefits of Breakthrough Designation and Fast Track designation, particularly benefits related to priority review, frequent communications with the FDA, and intensive guidance from the FDA, to the extent such benefits are applicable to any of our product candidates. Any of the above impacts could in turn delay our anticipated timelines, which can increase the cost of clinical development of our product candidates. Other policy changes may lead to fewer agency guidance documents,documents or to changes in our clinical development plans, which could result in changesdelays, toadditional FDA programs or possible delaysexpenses, or refusals to approve products. Further, FDA’s “real-time” release of newly issued Complete Response Letters associated with withdrawn or abandoned applications, if applicable to any of our product candidates, can materially impact our competitive advantage and intellectual property. It is unclear how our industry and our clinical programs will be impacted by policies or regulations implemented under the current administration and the new FDA commissioner or other executive orders. To the extent the agency'sagency’s reduction in force and other agency changes lead to disruptions in the FDA’s operations, our interactions, correspondence, and regulatory review processes with the FDA may be delayed.

Further, the current administration has issued executive orders focused on decreasing prescription drug prices, including directing the Secretary of Health and Human Services to establish a mechanism through which American patients can buy drugs directly from manufacturers who sell at a most-favored-nation (MFN) price and directing the U.S. Trade Representative and Secretary of Commerce to take action to ensure foreign countries are not engaged in practices that purposefully and unfairly undercut market prices and drive price hikes in the United States. The OBBBA includes provisions that will impact the U.S. healthcare system in various ways, including by cuts to Medicaid and introducing new participant work and eligibility requirements for Medicaid coverage, which are expected to significantly change the administration and applicability of Medicaid coverage. In November 2025, CMS announced a voluntary initiative called the GENEROUS Model (GENErating cost Reductions fOr U.S. Medicaid Model) to introduce the option of most-favored-nation pricing to the Medicaid program, whereby a drug manufacturer may voluntarily offer supplemental rebates to participating state Medicaid programs for a manufacturer’s covered outpatient drugs. In June 2026, CMS issued a proposed rule that would codify policies established in guidance documents for the Medicare Drug Price Negotiation Program for initial price applicability year 2029 and beyond. CMS plans to release additional guidance to implement policies related to the effectuation of the maximum fair price for the Medicare Drug Price Negotiation Program for 2028, consistent with the Inflation Reduction Act.

We currentlyhave useused and expectmay toin continuethe tofuture use third-party collaborators for the research, development, and commercialization of certain of the product candidates we may develop, including our arrangements with GSK, Adimab, and previously,those AbbVie.collaborations Asmay discussednot previously,be successful. On July 6, 2026, GSK canprovided terminatewritten notice to the Company terminating the GSK AgreementAgreement, withfollowing us,the subjectdiscontinuation toof certainthe noticedevelopment provisions,of in its entiretylatozinemab and nivisnebart based on the results of the INFRONT-3 Phase 3 clinical trial and the PROGRESS-AD Phase 2 interim analysis for conveniencethose atproduct anycandidates, time.respectively. Adimab can terminate its agreement with us in the event of our uncured materials breaches, and subject to certain notice requirements. In January 2025, AbbVie decided to terminate the AbbVie Agreement after the INVOKE-2 Phase 2 clinical trial evaluating the safety and efficacy of AL002 in slowing disease progression in individuals with early AD failed to meet the primary endpoint. In the event that anotherany of our current third-party collaborators discontinues its collaboration with us, we may not be able to find a suitable alternative collaboration partner or partners, or we may need to obtain and expend additional and unanticipated capital to maintain our current development programs.

We may not realize the benefit of collaborations if we or our collaborator are unable to successfully develop a product candidate and commercialize it upon approval or integrate a product candidate into existing operations and company culture. For example, in January 2025, AbbVie decided to terminate the TREM2 collaboration program, which resulted in termination of the AbbVie Agreement, after the INVOKE-2 Phase 2 clinical trial evaluating the safety and efficacy of AL002 in slowing disease progression in individuals with early AD failed to meet the primary endpoint. Therefore, we did not receive a $250.0 million milestone payment for AbbVie’s opting into the AL002 program or any future payments, and all rights to the TREM2 program have reverted back to us. In October 2025, we announced that latozinemab failed to meet the clinical co-primary endpoint in the INFRONT-3 Phase 3 clinical trial. As a result, we will not be seeking approval for and commercializing latozinemab in FTD-GRN, and certain milestone payments ($160 million for the first US commercial sale and $90 million for the first commercial sale in two or more EU countries) will not be achieved through commercialization of latozinemab in FTD-GRN, and our receipt of such milestones will therefore be delayed, or may not occur at all. On July 6, 2026, GSK provided written notice to the Company terminating the GSK Agreement. Therefore we will not receive up to an additional $1.5 billion in clinical development, regulatory, and commercial launch-related milestone payments, an equal share of profits and losses in the United States, and tiered royalties outside the United States, as we had been eligible for under that agreement.

We contract with third parties for the manufacture of materials for our research programs, preclinical studies, clinical trials, and for commercialization of any product candidates that we may develop. Additionally, GSK, and other potential partners, currently have orpartners may in the future have certain product manufacturing rights under their respective agreements. This reliance on third parties carries and may increase the risk that we will not have sufficient quantities of such materials, product candidates, or any medicines that we may develop and commercialize, or that such supply will not be available to us at an acceptable cost, which could delay, prevent, or impair our development or commercialization efforts.

OurWe may rely on certain patent rights and proprietary technology from third parties that are important or necessary to the development of our product candidates, and development and commercialization of our product candidates may be subject to the terms and conditions of collaboration agreements with Adimab,third GSK,parties. and otherSuch agreements we enter into in the future may not provide exclusive rights to use certain intellectual property and technology retained by the collaborator in all relevant fields of use and in all territories in which we may wish to develop or commercialize our technology and products in the future. As a result, we may not be able to prevent competitors or other third parties from developing and commercializing competitive products that utilize technology retained by such collaborators to the extent such products are not also covered by our intellectual property. In addition, subject to the terms of any such agreements, we may not have the right to control the preparation, filing, prosecution, and maintenance, and we may not have the right to control the enforcement and defense of certain patents and patent applications relating to or affecting our development candidates.

In addition, each of our agreements with collaborators do, and we expect our future agreements will, impose various economic, development, diligence, commercialization, and other obligations on us. Certain of our collaboration agreements alsomay require us to meet development timelines, or to exercise commercially reasonable efforts to develop and commercialize licensed products. In spite of our efforts, our collaborators might conclude that we have materially breached our obligations under such agreements and might therefore terminate or seek damages under the agreements, thereby removing or limiting our ability to develop and commercialize products and technology covered by these agreements. If termination of these agreements causes us to lose the rights to certain patents or other intellectual property, or if the underlying patents fail to provide the intended exclusivity, competitors or other third parties may have the freedom to seek regulatory approval of, and to market, products similar to or identical to ours and we may be required to cease our development and commercialization of certain of our product candidates. Any of the foregoing could have a material adverse effect on our competitive position, business, financial conditions, results of operations, and growth prospects.

Our near-term financial performance and development plans also require that we manage our personnel, and in each of 2024 and 2025 we committed to plans to reduce our workforce to better align our resources with our strategic priorities. We initiated a reduction in force in October 2025 that impacted approximately 47% of our workforce. Total incremental restructuring charges associated with the reduction in force are approximately $7.0 million, consisting primarily of severance and related termination benefits. Cash payments related to these expenses will bewere paid out during the first half of 2026. We previously initiated reductions in force effective March 2025 and effective November 2024.

We have experienced cyberattacks in the past that have not had a material effect on our business operations, and we face the risk of future cyberattacks that may or may not have a material effect. Despite the implementation of security measures, our internal computer systems and those of third parties with which we engage, such as research institution collaborators, clinical trial sites, and CROs and other vendors, contractors and consultants, may be vulnerable to damage, interruption, or other disruption from various causes, including computer viruses and other malicious code, and may be vulnerable to unauthorized access. Likewise, data privacy or security breaches or incidents, or breaches or other incidents undertaken or otherwise caused by employees or others, may pose a risk that sensitive data, including our intellectual property, trade secrets, or personal information of our employees, patients, customers, or other business partners, may be exposed to unauthorized persons or to the public or may otherwise be misused. As the cyber-threat landscape evolves, especially as certain of our employees have engaged in remote or hybrid work and bad actors use AI to automatautomate attacks, these attacks are growing in frequency, sophistication, and intensity, and are becoming increasingly difficult to detect, mitigate, and defend against. Such threats are prevalent andprevalent, continue to rise, are increasingly difficult to detect, and come from a variety of sources, including traditional computer “hackers,” threat actors, “hacktivists,” organized criminal threat actors, personnel (such as through theft or misuse), sophisticated nation states, and nation-state-supported actors. During times of war and other conflicts, we and our business counterparties, including third parties upon which we rely, may be vulnerable to a heightened risk of these attacks. Such attacks might involve the use of sophisticated malware, including ransomware or various types of service denial tactics. They can be initiated through harmful websites or by leveraging phishing strategies, social engineering tactics, or credential stuffing. This might also include brute force attacks, along with other contemporary malicious methods which are always changing.

If a breakdown, cyberattack, or other information security breach or incident occurs, it could cause damage to or interruptions or other disruptions in our operations or those of third parties, with which we engage, and could result in damage to, the loss or unavailability of, or misappropriation or other unauthorized use or processing of, sensitive data, including personal information and confidential information, such as our intellectual property or financial information, and a material disruption of our research and development programs and our business operations.operations could result. For example, the loss or unavailability of, or damage to, clinical trial data from completed, ongoing, or future clinical trials could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. Likewise, we rely on third-party research institution and collaborators, clinical trial sites, and CROs and other vendors, consultants and contractors for research and development of our product candidates, and we rely on other third parties, such as CDMOs and CROs, to manufacture our product candidates and to conduct clinical trials, respectively. Supply-chain attacks against third-party actors like these have increased in frequency and severity, and we cannot guarantee that third-party infrastructure in our supply chain or our third-party partners’ supply chains have not been or will not be compromised. Cyberattacks, security breaches and incidents, and disruptions, interruptions, and similar events relating to their computer systems and operations could also have a material adverse effect on our business.

The majority of our operations including our corporate headquarters are located in a facility in South San Francisco, California. Damage or extended periods of interruption to our corporate, development, or research facilities due to fire, natural disaster, global pandemics, power loss, communications failure, unauthorized entry, earthquakes or other events that impact the use of our facilities could cause us to cease or delay development of some or all of our product candidates. Although we maintain property damage and business interruption insurance coverage on these facilities, our insurance might not cover all losses under such circumstances, and our business may be seriously harmed by such delays and interruption.

negative consequences from changes in tax laws; (including the provisions of the federal tax legislation titled the Inflation Reduction Act);

These and other risks associated with our planned international operations may materially adversely affect our ability to attain profitable operations. Further, there is currently significant uncertainty about the current presidential administration’s policies and priorities, which could affect future relationships between the United States and various other countries, most significantly China, the European Union, and other trading partners, with respect to trade policies, treaties, tariffs, taxes, and other limitations on cross-border operations. For example, the National Defense Authorization Act of 2026, which includes Section 851 regarding the prohibition on contracting with certain biotechnology providers (“the BIOSECURE Act”), may ultimately limit certain U.S. biotechnology companies from using equipment or services produced or provided by Chinese biotechnology companies or their affiliates that meet the designation criteria of the new law. Moreover, both the United States and China have implemented significant trade tariffs against each other’s imports. Separately, a Department of Justice rule effective in April 2025, along with subsequent action by the FDA, prohibits or restricts transfer of sensitive personal data, including health data, biometric data, and human genomic data, and patient biological materials to China and other “countries of concern” in the interests of national security. As a result of these and other laws and regulationsregulations, or the impact on trade relations between the United States and China or other countries, our business may be seriously harmed if we are unable to obtain or use services or products from existing service providers, including those of contract development and manufacturing organizations, or if alternative service providers cannot be secured at an acceptable cost or at all. Likewise, if foreign policy measures, such as those described above, cause broader disruption in drug manufacturing and related industries that impact drug development, clinical trials, and drug product availability or pricing, then our business, liquidity, financial condition, and/or results of operations would be materially and adversely affected.

Sales of a substantial number of shares of our common stock in the public market could occur at any time. If our stockholders sell, or the market perceives that our stockholders intend to sell, substantial amountamounts of our common stock in the public market, the market price of our common stock could decline significantly.

Our common stock is currently listed for trading on The Nasdaq Global Select Market. We must satisfy Nasdaq’s continued listing requirements, including a minimum bid price for our common stock of $1.00 per share. Given the current market environment and despite our cash position, our common stock has traded for less than $1.00 per share during the second quarter of 2025, and our aggregate market capitalization at various times over the last several quarters has valued below the total value of our cash, cash equivalents, and investments. If we do not meet these requirements, we risk possible delisting from Nasdaq, which could have a material adverse effect on our business.

We may seek additional capital through a combination of public and private equity offerings, debt financings, strategic partnerships and alliances, and licensing arrangements. We, and indirectly, our stockholders, will bear the cost of issuing and servicing such securities. Because our decision to issue debt or equity securities in any future offering will depend on market conditions and other factors beyond our control, we cannot predict or estimate the amount, timing, or nature of any future offerings. To the extent that we raise additional capital through the sale of equity or debt securities, the ownership interest of stockholders will be diluted, and the terms may include liquidation or other preferences that adversely affect the rights of stockholders. The incurrence of indebtedness would result in increased fixed payment obligations and could involve restrictive covenants, such as limitations on our ability to incur additional debt, limitations on our ability to acquire, sell, or license intellectual property rightsrights, and other operating restrictions that could adversely impact our ability to conduct our business. We have an omnibus shelf registration statement on Form S-3 with the SEC, which became effective on April 30, 2026, which permits us to issue up to $400 million in common stock, other equity securities and/or debt securities.

On November 7, 2023, we entered into an at-the-market sales agreement with TD Securities (USA) LLC (TD Securities,LLC, formerly known as Cowen and Company, LLC (TD Cowen) pursuant to which we may offer and sell from time to time through TD SecuritiesCowen up to $125,000,000 of shares of our common stock (the Placement Shares),stock, in such share amounts as we may specify by notice to TD Securities (the 2023 Sales Agreement). As of MarchJune 31,30, 2026, we have issued 7,110,162 shares and received approximately $20.0 million in net proceeds from the sale of securities pursuant to the 2023 Sales Agreement. The Sales Agreement includes a renewal provision pursuant to which we may file a new shelf registration statement relating to the Placement Shares. On January 17, 2024, we entered into an underwriting agreement with Cantor, pursuant to which we offered and sold 10,869,566 shares of the Company’s common stock at a price per share of $6.57 paid by Cantor. Additionally, any future collaborations we enter into with third parties may provide capital in the near term but limit our potential cash flow and revenue in the future. If we raise additional funds through strategic partnerships and alliances and licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies or product candidates, or grant licenses on terms unfavorable to us.

Additionally, on November 14, 2024, we entered into the Loan Agreement with Lenders and Hercules pursuant to which we maycould access up to two tranches of term loans in an aggregate principal amount of up to $50,000,000. The initial tranche of Term Loans provides for an aggregate principal amount of up to $25,000,000 through June 30, 2026,$50,000,000, subject to the satisfaction of certain conditions. The second tranche of Term Loans provides for up to $25,000,000 and is available at the sole discretion of the Lenders. We borrowed $10,000,000 principal amount of the initialfirst tranche of Term Loans on the closing date of the Loan Agreement. On July 8, 2026, the Company entered into a payoff letter with Hercules and paid the final payoff amount. All obligations under the Loan Agreement were paid in full, all liens and security interests granted to secure such obligations were terminated, and the Loan Agreement and related loan documents were terminated.

Our directors, executive officers, holders of more than 5% of our outstanding stock and their respective affiliates beneficially own 28.4%22.5% of our outstanding common stock as of MayJuly 1,31, 2026. As a result, these stockholders, if they act together, may significantly influence all matters requiring stockholder approval, including the election of directors and approval of significant corporate transactions. This concentration of ownership may have the effect of delaying or preventing a change in control of our company that our other stockholders may believe is in their best interests. This in turn could have a material adverse effect on our stock price and may prevent attempts by our stockholders to replace or remove the board of directors or management.

As a public company, we have incurred and will continue to incur significant legal, accounting, and other expenses that we did not incur as a private company. The Sarbanes-Oxley Act, the Dodd-Frank Wall Street Reform, and Consumer Protection Act, the listing requirements of Nasdaq, and other applicable securities rules and regulations impose various requirements on public companies, including establishment and maintenance of effective disclosure and financial controls and corporate governance practices. We have hired, and expect that we will need to continue to hire, additionalhired accounting, finance, and other personnel in connection with our being, and our efforts to comply with the requirements of being, a public company, and our management and other personnel have devoted and will continue to devote a substantial amount of time towards maintaining compliance with these requirements. These requirements have increased and will continue to increase our legal and financial compliance costs and will make some activities more time-consuming and costly. For example, we expect that the rules and regulations applicable to us as a public company may make it more difficult and more expensive for us to maintain director and officer liability insurance, which could make it more difficult for us to attract and retain qualified members of our board of directors. We are currently evaluating these rules and regulations and cannot predict or estimate the amount of additional costs we may incur or the timing of such costs. These rules and regulations are often subject to varying interpretations, in many cases due to their lack of specificity, and, as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies. This could result in continuing uncertainty regarding compliance matters and higher costs necessitated by ongoing revisions to disclosure and governance practices.

Investors should not rely on an investment in our common stock to provide dividend income. We do not anticipate that we will pay any dividends to holders of our common stock in the foreseeable future. Instead, we plan to retain any earnings to maintain and expand our existing operations. In addition, any future credit facility may contain terms prohibiting or limiting the amount of dividends that may be declared or paid on our common stock. Accordingly, investors must rely on sales of their common stock after price appreciation, which may never occur, as the only way to realize any return on their investment. We are also prohibited from declaring or paying any cash dividends under our Loan Agreement. As a result, investors seeking cash dividends should not purchase our common stock.

AL037/AL137 Program

Following comparative evaluation of AL137 and AL037, we selected AL137 as the lead development candidate and subcutaneous administration as the intended clinical route, with AL037 designated as the backup development candidate. Following successful completion of IND-enabling studies, we intend to select AL037 oradvance AL137 for submission of an Investigational New Drug (IND) application, targeted for the first quarter of 2027. We also target first-in-human dosing in Australia no later than April 2027.

AL050 is a lysosomal glucocerebrosidase (GCase) enzyme replacement therapy paired with our proprietary ABC technology in preclinical development for Parkinson’s disease and Lewy body dementia in patients having GBA1 gene mutations that lead to reduced GCase activity. AL050 features an engineered GCase with improved activity and stability, a silenced effector function to maximize safety, and Alector’s ABC withthat binds a TfR epitope andwith affinity designed to enhance delivery across the BBB. This mechanism aims to reduce cellular dysfunction and slow disease progression. In preclinical studies to date, AL050 doubled GCase activity in different brain regions in non-human primates without observed adverse effects, including hematologic effects. In a GBA disease mouse model, AL050 surrogate rescued GCase activity and reduced toxic substrate accumulation without abnormal hematologic findings. These data support the potential of AL050 as a disease modifying therapy for Parkinson’s disease (PD) and Lewy body dementia (LBD) associated with GBA loss of function mutations, and subsequently for idiopathic PD and LBD.

We have selected AL050 as athe lead candidate, and we continue to evaluate our timeline to the clinic.

In April 2026, GSK discontinued the global Phase 2 PROGRESS-AD trial of nivisnebart (AL101/GSK4527226), an investigational progranulin-elevating monoclonal antibody, in individuals with early Alzheimer'sAlzheimer’s disease (AD), afterfollowing a pre-specified interim futility analysis conducted by an Independent Data Monitoring Committee (IDMC),. whichThe IDMC concluded that the trial was unlikely to meet its primary endpoint of slowing disease progression at completion.

Our operations have been financed primarily through our collaboration with GSK, for which GSK provided written notice of termination on July 6, 2026, our previous collaboration with AbbVie, entered into in October 2017 and terminated in February 2025, the issuance and sale of convertible preferred stock and of common stock upon the completion of our initial public offering (IPO), and follow-on equity financings.

To date, we have not had any products approved for sale and have not generated any product or royalty revenue from product sales. Further, we do not expect to generate revenue from product sales until such time, if ever, that we are able to successfully complete the development and obtain marketing approval for one of our product candidates. We will continue to require additional capital to develop our product candidates, advance our research and preclinical programs, and fund operations for the foreseeable future. We have incurred net losses in each year since inception, and we expect to continue to incur net losses for the foreseeable future. Our ability to generate product revenue will depend on the successful development and eventual commercialization of one or more of our product candidates. Our net losses were $22.9$23.0 million and $40.5$45.9 million for the three and six months ended MarchJune 31,30, 20262026, respectively. Our net losses were $30.5 million and $71.0 million for the three and six months ended June 30, 2025, respectively. As of MarchJune 31,30, 2026, we had an accumulated deficit of $995.0$1,018.0 million. Substantially all of our net losses have resulted from costs incurred in connection with our research and development programs and from general and administrative costs associated with our operations. We expect our expenses will increase substantially in connection with our ongoing activities, as we:

On March 7, 2025, we committed to a plan to reduce our workforce by approximately 13% to better align our resources with our strategic priorities, including the advancement of our preclinical and research pipeline. We initiated that reduction in force impacting approximately 25 employees across the organization. On October 21, 2025, we committed to a plan to reduce our workforce by approximately 47% in order to align resources with the Company’s strategic priorities following the results of the Phase 3 INFRONT-3 clinical trial evaluating the safety and efficacy of latozinemab (AL001) in individuals with frontotemporal dementia due to a GRN mutation (FTD-GRN). Our cash, cash equivalents, and marketable securities as of MarchJune 31,30, 2026, totaled $206.5$172.8 million, which we anticipate provides runway at least through 2027.

Under the terms of the GSK Agreement, wethe Company received $700 million in upfront payments, of which $500 million was received in August 2021 and $200 million was received in January 2022. InThe addition,Company wehad may bebeen eligible tofor receivebut did not achieve up to an additional $1.5 billion in clinical development, regulatory, and commercial launch-related milestone payments,payments; an equal share of profits and losses in the United States; and tiered royalties outside the United States. The Company and GSK jointly conducted certain development activities under the Agreement and shared development costs 60% by GSK and 40% by the Company, except that, subject to successful advancement and commercialization of product candidates in multiple indications under the agreement. Alector and GSK are conducting development jointly. In May 2023, we and GSK amended the GSK Agreement.Amendment, the Company solely bore the development costs of initial Phase 2 clinical trials. Under the terms of the GSK Amendment, wethe areCompany was responsible for funding and sharing in GSK’s and ourthe Company’s development costs up to $140.5 million for the conduct of the Phase 2 clinical trial of nivisnebart in AD.

We expect that our revenue will be derived primarily from the GSK Agreement.Agreement in the near term. The balance of deferred revenue was $169.6$162.9 million as of MarchJune 31,30, 2026, related to the GSK Agreement. TheAs deferredof revenuethat isdate, the Company expected to berecognize recognizedthis deferred revenue over the research and development period of the programs through the completion of the initial Phase 2 clinical trials for specified indications for latozinemab and nivisnebart.nivisnebart, or earlier upon extinguishment of the related performance obligations.

Specific program expenses include expenses associated with the development of our product candidate, nivisnebart, which was being studied in the PROGRESS-AD Phase 2 clinical trial. That trial has been discontinued following a pre-specified interim futility analysis, in which an independent data monitoring committeeIDMC concluded that the trial was unlikely to meet its primary endpoint of slowing disease progression at completion. We also have expenses related to the research and development of future product candidates and separately tracked expenses related to programs that we expect to move out of preclinical studies and into Phase 1 clinical trials. These expenses primarily relate to salaries and benefits, stock-based compensation, facility expenses, including depreciation, and lab consumables.

At this time, we cannot reasonably estimate or know the nature, timing, and estimated costs of the efforts that will be necessary to complete the development of, and obtain regulatory approval for, any of our product candidates. We expect our research and development expenses relating to latozinemablatozinemab, nivisnebart, and AL002 to decrease in the foreseeable future as a result of the discontinuation and wind-down of clinical trials for latozinemablatozinemab, nivisnebart, and AL002. However, we continue to invest in research and development activities related to programs in our research and preclinical pipeline and to the advancement of those programs into clinical trials.

Comparison of the Three Months Ended MarchJune 31,30, 2026 and 2025

Collaboration revenue was $1.0$3.3 million for the three months ended MarchJune 31,30, 2026, compared to $3.6$7.9 million for the three months ended MarchJune 31,30, 2025. The $2.6$4.6 million decrease was primarily attributabledue to a lower manufacturing-relatedrevenue activityrecognized to supportfor the NivisnebartAL101 PhaseAD 2 study in early Alzheimer’s disease during the current period.program. Revenues are recognized as the program costs are incurred by measuring actual costs incurred to date compared to the overall total expected costs to satisfy each performance obligation.

Research and development expenses were $17.8$19.5 million for the three months ended MarchJune 31,30, 2026, compared to $33.6$27.6 million for the three months ended MarchJune 31,30, 2025. The decrease of $15.8$8.1 million was mainly due to a decrease in personnel-related costs as a result of the reductions in force as well as a decrease in researchfacilities and developmentother expenses for the AL002 program.expenses.

General and administrative expenses were $8.1$8.3 million for the three months ended MarchJune 31,30, 2026 and $14.7$14.4 million for the three months ended MarchJune 31,30, 2025. The decrease of $6.6$6.1 million was mainly driven by a decrease in personnel-related costs as a result of the reductions in force.

Other income, net was $2.0$1.5 million for the three months ended MarchJune 31,30, 2026, compared to $4.2$3.6 million for the three months ended MarchJune 31,30, 2025. The decrease of $2.2$2.1 million was mainly due to lower interest income from a reduction in marketable securities used to fund our operations.

Since our inception through MarchJune 31,30, 2026, our operations have been financed primarily by our collaborations with GSK, and previously, AbbVie, the issuance and sale of convertible preferred stock and of common stock upon the completion of our IPO andIPO, follow-on equity, and debt financings.

As of MarchJune 31,30, 2026, we had $206.5$172.8 million of cash, cash equivalents, and marketable securities. As of MarchJune 31,30, 2026, we had an accumulated deficit of $995.0$1,018.0 million.

Our primary uses of cash are to fund our operations, which consist primarily of research and development expenditures related to our programs, and to a lesser extent, general and administrative expenditures. We expect our expenses relating to latozinemabnivisnebart, latozinemab, and AL002 to decrease in the foreseeable future as a result of the discontinuation and wind-down of clinical trials for latozinemabnivisnebart, latozinemab, and AL002. However, we continue to invest in research and development activities related to programs in our research and preclinical pipeline and the advancement of those programs into clinical trials. In addition, we expect to incur costs associated with operating as a public company.

On November 7, 2023, we entered into an at-the-market sales agreement with TD Securities (USA) LLC (TD Securities, formerly known as Cowen and Company, LLC)Cowen, pursuant to which we may offer and sell from time to time through TD SecuritiesCowen up to $125,000,000 of shares of our common stock (the Placement Shares),stock, in such share amounts as we may specify by notice to TD SecuritiesCowen (the 2023 Sales Agreement). As of MarchJune 31,30, 2026, we havehad issued an aggregate of 7,110,162 shares and received approximately $20$20.0 million in net proceeds fromunder the sale2023 Sales Agreement, all of securities pursuant to the Sales Agreement. The Sales Agreement includes a renewal provision pursuant to which wewere mayissued fileduring a new shelf registration statement relating to the Placement Shares.2025.

On January 17, 2024, we entered into an underwriting agreement with Cantor Fitzgerald & Co. (Cantor), pursuant to which we offered and sold 10,869,566 shares of the Company’s common stock at a price per share of $6.57 paid by Cantor. Additionally, on November 14, 2024, we entered into a loan agreement with our subsidiary, Alector LLC, as a co-borrower, the Lenders, and Hercules Capital, Inc.,Inc. (Hercules), in its capacity as administrative agent and collateral agent for itself and the Lenders (the Loan Agreement), pursuant to which we maycould access up to two tranches of Term Loans in an aggregate principal amount of up to $50,000,000. The initial tranche of Term Loans provides for an aggregate principal amount of up to $25,000,000 through June 30, 2026,$50,000,000, subject to the satisfaction of certain conditions. The second tranche of Term Loans provides for up to $25,000,000 and is available at the sole discretion of the Lenders. We borrowed $10,000,000 principal amount of the initialfirst tranche of Term Loans on the closing date of the Loan Agreement. On July 8, 2026, the Company entered into a payoff letter with Hercules and paid the final payoff amount. All obligations under the Loan Agreement were paid in full, all liens and security interests granted to secure such obligations were terminated, and the Loan Agreement and related loan documents were terminated.

the timing and progress of preclinical and clinical development activities; including, without limitation, our collaboration efforts with GSK;

the timing and amount of milestone and other payments we may receive under ourany collaboration arrangements;

For the threesix months ended MarchJune 31,30, 2026, cash used in operating activities was $49.8$84.0 million. This was mainly due to the net loss of $22.9$45.9 million. We also had a decrease in refund liability to collaboration partner of $12.0$15.4 million, a decrease in accrued liabilities and accrued clinical supply costs of $11.0$13.8 million, and a decrease in collaboration payable of $13.6 million. This was offset by a non-cash charge of $2.9$5.5 million for stock-based compensation.

For the threesix months ended MarchJune 31,30, 2025, cash used in operating activities was $60.8$109.8 million. This was mainly due to the net loss of $40.5$71.0 million. We also had a decrease in refund liability to collaboration partner of $13.3$26.1 million, a decrease in deferred revenue of $11.5 million, and a decrease in accrued liabilities and accrued clinical supply costs of $12.7$16.5 million. This was offset by a non-cash charge of $8.4$15.4 million for stock-based compensation.

For the threesix months ended MarchJune 31,30, 2026, cash provided by investing activities of $60.9$78.0 million was primarily related to the maturities of marketable securities of $112.9$157.9 million offset by purchases of marketable securities of $51.8$79.7 million.

For the threesix months ended MarchJune 31,30, 2025, cash provided by investing activities of $65.7$121.5 million was primarily related to the maturities of marketable securities of $121.5$250.4 million offset by purchases of marketable securities of $55.8$131.9 million.

For the threesix months ended MarchJune 31,30, 2026, cash provided by financing activities of less than $0.1 million was from the proceeds from the exercise of options to purchase common stock.stock and the purchase of common stock under the employee stock purchase plan.