Lineage Cell Therapeutics : Prospectus disclosing information, facts, events

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-277758

PROSPECTUS SUPPLEMENT

(To prospectus dated May 14, 2024)

Up to $39,966,424 Common Shares

We have entered into a sales agreement (the "sales agreement") with B. Riley Securities, Inc. ("B. Riley") relating to the sale of our common shares offered by this prospectus supplement and the accompanying prospectus. We may offer and sell common shares having an aggregate offering price of up to $39,966,424, from time to time through or to B. Riley as sales agent or principal.

Our common shares trade on the NYSE American and on the Tel Aviv Stock Exchange under the symbol "LCTX." On May 10, 2024, the last reported sale price of our common shares on the NYSE American was $1.17 per share.

Sales of our common shares, if any, under this prospectus supplement and the accompanying prospectus will be made by any method that is deemed an "at the market offering" as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the "Securities Act"). B. Riley is not required to sell any specific number or dollar amount of securities, but will act as a sales agent in connection with agency transactions using commercially reasonable efforts to sell on our behalf all of the common shares requested to be sold by us, consistent with its normal trading and sales practices, on mutually agreed terms between B. Riley and us. In addition, B. Riley may act as principal in connection with any principal transactions. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

B. Riley will be entitled to a commission of up to 3.0% of the gross sales price per share sold under the sales agreement. In connection with the sale of the common shares on our behalf, B. Riley will be deemed to be an "underwriter" within the meaning of the Securities Act, and the compensation of B. Riley will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to B. Riley with respect to certain liabilities, including liabilities under the Securities Act.

Investing in our securities involves a high degree of risk. You should carefully review the risks and uncertainties described under the heading "Risk Factors" on page S-4 of this prospectus supplement and under similar headings in the other documents that are incorporated by reference into this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

B. Riley Securities

The date of this prospectus supplement is May 14, 2024.

TABLE OF CONTENTS
Prospectus Supplement
ABOUT THIS PROSPECTUS SUPPLEMENT	S-i
PROSPECTUS SUPPLEMENT SUMMARY	S-1
THE OFFERING	S-3
RISK FACTORS	S-4
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS	S-5
USE OF PROCEEDS	S-6
DILUTION	S-6
PLAN OF DISTRIBUTION	S-7
LEGAL MATTERS	S-8
EXPERTS	S-8
WHERE YOU CAN FIND MORE INFORMATION	S-8
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	S-9
Prospectus dated May 14, 2024
ABOUT THIS PROSPECTUS	i
PROSPECTUS SUMMARY	1
RISK FACTORS	5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS	5
USE OF PROCEEDS	6
DESCRIPTION OF CAPITAL STOCK	6
DESCRIPTION OF DEBT SECURITIES	8
DESCRIPTION OF WARRANTS	14
PLAN OF DISTRIBUTION	18
LEGAL MATTERS	20
EXPERTS	20
WHERE YOU CAN FIND MORE INFORMATION	20
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	21

ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying prospectus relate to the offering of our common shares. You should read this prospectus supplement, the accompanying prospectus, the documents incorporated by reference into this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we may authorize for use in connection with this offering in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus supplement entitled, "Where You Can Find More Information" and "Incorporation of Certain Information by Reference." These documents contain important information that you should consider when making your investment decision.

This prospectus supplement and the accompanying prospectus are part of a "shelf" registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the "SEC"). This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of the offering of our common shares and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus, including the documents incorporated by reference into the accompanying prospectus, provides more general information, some of which may not apply to the offering. Generally, when we refer to this prospectus, we are referring to the combined document consisting of this prospectus supplement and the accompanying prospectus. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or in any document incorporated by reference into the accompanying prospectus that was filed with the SEC before the date of this prospectus supplement, on the other hand, you should rely on the information in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date, the statement in the document having the later date modifies or supersedes the earlier statement.

You should rely only on the information contained in, or incorporated by reference into, this prospectus supplement, the accompanying prospectus and in any free writing prospectus that we may authorize for use in connection with this offering. We have not, and the sales agent has not, authorized anyone to provide you with different information, and neither we nor the sales agent take any responsibility for any other information that others may give you.

We and the sales agent are not making an offer to sell or soliciting an offer to buy our securities in any jurisdiction in which an offer or solicitation is not authorized or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation.

You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference into this prospectus supplement and the accompanying prospectus, and in any free writing prospectus that we may authorize for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

This prospectus supplement, the accompanying prospectus, and the information incorporated herein and therein by reference includes trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks or trade names appearing in or incorporated by reference into this prospectus supplement or the accompanying prospectus are the property of their respective owners. Solely for convenience, the trademarks, service marks and trade names appearing in or incorporated by reference into this prospectus supplement or the accompanying prospectus may be referred to without the symbols "®" and "™", but such references should not be construed as any indication that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto. Use or display by us of other parties' trademarks, service marks or trade names is not intended to and does not imply a relationship with, or endorsements or sponsorship of, us by the trademark, service mark or trade name owners.

The representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference into this prospectus supplement or the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

Unless otherwise indicated, information contained in this prospectus supplement, the accompanying prospectus, and in the documents we incorporate by reference herein and therein concerning our industry and the markets in which we operate, including our general expectations and market position, market opportunity and market size, is based on information from various sources, including peer reviewed journals, formal presentations at medical and scientific society meetings and third-parties commissioned by us or our licensors to provide market research and analysis, and is subject to a number of assumptions and limitations. Although we are responsible for all of the disclosure contained in this prospectus supplement, the accompanying prospectus, and in the documents we incorporate by reference, and we believe the information from industry publications and other third-party sources included herein and therein is reliable, such information is inherently imprecise. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances that are assumed in this information. The industry in which we operate is subject to a high degree of uncertainty and risk due to a variety of factors.

Unless the context otherwise requires, "Lineage," "the Company," "we," "us," "our" and similar terms refer to Lineage Cell Therapeutics, Inc. and its consolidated subsidiaries. When we refer to "you" we mean potential holders of the securities we may offer under this prospectus supplement and accompanying prospectus.

(i)

PROSPECTUS SUPPLEMENT SUMMARY

The following summary highlights selected information contained elsewhere in or incorporated by reference into this prospectus supplement. This summary is not complete and does not contain all of the information that you need to consider in making your investment decision. You should carefully read this entire prospectus supplement, the accompanying prospectus and any related free writing prospectus, including the risks of investing in our securities discussed under the heading "Risk Factors" in this prospectus supplement and in any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus supplement, the accompanying prospectus and any related free writing prospectus. You should also carefully read the information incorporated by reference into this prospectus supplement, including our financial statements, and the exhibits to the registration statement of which this prospectus supplement is a part.

Overview

We are a clinical-stage biotechnology company developing novel allogeneic, or "off-the-shelf," cell therapies to address unmet medical needs. Our programs are based on our proprietary cell-based technology platform and associated development and manufacturing capabilities. From this platform, we design, develop, manufacture, and test specialized human cells with anatomical and physiological functions similar or identical to cells found naturally in the human body. The cells we manufacture are created by applying directed differentiation protocols to established, well-characterized, and self-renewing pluripotent cell lines. These protocols generate cells with characteristics associated with specific and desired developmental lineages. Cells derived from such lineages which are relevant to the underlying condition are transplanted into patients in an effort to (a) replace or support cells that are absent or dysfunctional due to degenerative disease, aging, or traumatic injury, and (b) restore or augment the patient's functional activity.

Our business strategy is to efficiently leverage our technology platform and our development, formulation, delivery, and manufacturing capabilities to advance our programs internally or in conjunction with strategic partners to further enhance their value and probability of success.

A significant area of focus is a collaboration we entered into with F. Hoffmann-La Roche Ltd and Genentech, Inc., a member of the Roche Group (collectively or individually, "Roche" or "Genentech"), under which our lead cell therapy program known as OpRegen®, is being developed for the treatment of ocular disorders, including geographic atrophy ("GA") secondary to age-related macular degeneration ("AMD"). OpRegen (also known as RG6501) is a suspension of human allogeneic retinal pigmented epithelial ("RPE") cells and is currently being evaluated in a Phase 2a multicenter clinical trial in patients with GA secondary to AMD. OpRegen subretinal delivery has the potential to counteract RPE cell loss in areas of GA lesions by supporting retinal cell health and improving retinal structure and function. Under the terms of the Collaboration and License Agreement we entered into with Roche in December 2021, we received a $50.0 million upfront payment in January 2022 and are eligible to receive up to an additional $620.0 million in developmental, regulatory, and commercialization milestone payments. We also are eligible to receive tiered double-digit percentage royalties on net sales of OpRegen in the U.S. and other major markets. On May 7, 2024, we entered into a service agreement with Genentech pursuant to which we will provide supplemental clinical, technical, training, manufacturing, and procurement services to support the ongoing advancement and optimization of the OpRegen program.

Our most advanced unpartnered product candidate is OPC1, an allogeneic oligodendrocyte progenitor cell therapy designed to improve recovery following a spinal cord injury ("SCI"). OPC1 has been tested in two clinical trials to date; a five patient Phase 1 clinical trial in acute thoracic SCI, where all subjects are followed for at least 10 years, and a 25 patient Phase 1/2a multicenter clinical trial in subacute cervical SCI, where all subjects were evaluated for at least two years. Results from both studies have been published in the Journal of Neurosurgery Spine. OPC1 clinical development has been supported in part by a $14.3 million grant from the California Institute for Regenerative Medicine. In January 2024 we filed an Investigational New Drug ("IND") amendment for OPC1 as it relates to our proposed DOSED (Delivery of Oligodendrocyte Progenitor Cells for Spinal Cord Injury: Evaluation of a Novel Device) clinical study, to evaluate the safety and utility of a novel spinal cord delivery device to administer OPC1 to the spinal parenchyma in subacute and chronic SCI patients. We have received written correspondence from the FDA, advising us that due to significant workload and conflicting PDUFA priorities at the agency, its review of our IND amendment and the DOSED study protocol is still ongoing. We have also received information requests from the FDA, all of which we have responded to in a timely manner, and such responses have not involved any commitments to perform additional activities that would delay commencement of the DOSED study. We intend to continue to work closely with the FDA to respond to any additional information requests and/or feedback. In parallel, we continue to focus on customary trial preparations and related activities to support opening our first clinical study site for the DOSED study in the second quarter of 2024.

S-1

Our neuroscience focused pipeline of allogeneic, or "off-the-shelf", cell therapy programs currently includes:

• RG6501 (OpRegen), an allogeneic RPE cell replacement therapy currently in a Phase 2a multicenter, open-label, single arm clinical trial, being conducted by Roche, for the treatment of GA secondary to AMD, also known as atrophic or dry AMD.
• OPC1, an allogeneic oligodendrocyte progenitor cell therapy which will be evaluated in the DOSED clinical study, to test the safety and utility of a novel spinal cord delivery device in both subacute and chronic spinal cord injuries and continues to be evaluated in long-termfollow-up from a Phase 1/2a multicenter clinical trial for subacute cervical spinal cord injuries.
• ANP1, an allogeneic auditory neuron progenitor cell transplant currently in preclinical development for the treatment of debilitating hearing loss.
• PNC1, an allogeneic photoreceptor cell transplant currently in preclinical development for the treatment of vision loss due to photoreceptor dysfunction or damage.
• RND1, a novel hypoimmune induced pluripotent stem cell line being developed in collaboration with Eterna Therapeutics Inc., which will be evaluated for differentiation into cell transplant product candidates for central nervous system diseases and other neurology indications.

Other Programs

We have additional undisclosed product candidates being considered for development, and we may consider others, which cover a range of therapeutic areas and unmet medical needs. Generally, these product candidates are based on the same platform technology and employ a similar, guided cell differentiation and transplant approach as the product candidates described above, but in some cases may also include genetic modifications designed to enhance efficacy and/or safety profiles.

Our efforts to broaden the application of our cell therapy platform and support long-term growth include a strategic collaboration we entered into with Eterna. This reflects a portion of our corporate strategy to capitalize on our process development capabilities by combining them with cell engineering and/or editing technologies, to create novel cell therapies with potentially superior product profiles compared to currently marketed therapies, if any.

In addition to seeking to create value for shareholders by developing product candidates and advancing those candidates through clinical development, we also may seek to create value from our non-core intellectual property or related technologies and capabilities, through licensing collaborations and/or strategic transactions, such as our business development approach to our VAC dendritic cell therapy platform.

Implications of Being a Smaller Reporting Company

We are a "smaller reporting company" as defined in the Securities Exchange Act of 1934, as amended (the "Exchange Act"). To the extent that we continue to qualify as a smaller reporting company, we may take advantage of accommodations afforded to smaller reporting companies including: (i) not being required to comply with the auditor attestation requirements of Section 404(b) of the Sarbanes Oxley Act of 2002; (ii) scaled executive compensation disclosure requirements; and (iii) providing only two years of audited financial statements, instead of three years. We will qualify as a smaller reporting company: (i) until the fiscal year following the determination that the market value of our voting and non-voting common shares held by non-affiliates is more than $250 million measured on the last business day of our second fiscal quarter, or (ii) if our annual revenues are less than $100 million during the most recently completed fiscal year, until the fiscal year following the determination that the market value of our voting and non-voting common shares held by non-affiliates is more than $700 million measured on the last business day of our second fiscal quarter.

Corporate Information

We are incorporated in the State of California. Our common shares trade on the NYSE American and the Tel Aviv Stock Exchange under the symbol "LCTX." Our principal executive offices are at 2173 Salk Avenue, Suite 200, Carlsbad, California 92008, and our phone number at that address is [phone]. Our website address is www.lineagecell.com. The information on, or that can be accessed through our website is not part of this prospectus supplement.

S-2

	THE OFFERING
Common shares offered in this offering	Common shares having an aggregate offering price of up to $39,966,424.
Common shares to be outstanding after this offering	Up to 222,983,312 shares, after giving effect to the sale of 34,159,337 common
	shares in this offering at an offering price of $1.17 per share, which was the last
	reported sale price of our common shares on the NYSE American on May 10, 2024.
	The actual number of shares sold in this offering will vary depending on the price at
	which shares may be sold from time to time.
Plan of distribution	"At the market offering" that may be made from time to time through B. Riley, as
	agent or principal. See "Plan of Distribution."
Use of proceeds	We currently intend to use the net proceeds from this offering for working capital and
	general corporate purposes, including research and development expenses and capital
	expenditures. See "Use of Proceeds."
Risk factors	Investing in our common shares involves significant risks. See the "Risk Factors"
	section of	this prospectus supplement,	and under similar headings in other
	documents	incorporated by reference	into this prospectus supplement.
NYSE American symbol	"LCTX"

The number of our common shares to be outstanding after this offering is based on 188,823,975 common shares outstanding as of May 10, 2024, and excludes, as of that date, the following:

• 26,493,958 common shares issuable upon the exercise of outstanding stock options with a weighted average exercise price of $1.53 per share awarded under our 2021 Equity Incentive Plan, as amended (our "2021 Equity Incentive Plan"), our 2012 Equity Incentive Plan, as amended (together with our 2021 Equity Incentive Plan, our "equity incentive plans"), or outside of our equity incentive plans pursuant to approval by the independent members of our board of directors in reliance the exception for inducement grants to new employees under the NYSE American Company Guide;
• 501,032 common shares issuable upon vesting and settlement of outstanding restricted stock units under our equity incentive plans; and
• 22,122,497 common shares available for future grant under our 2021 Equity Incentive Plan.

Except as otherwise indicated, all information in this prospectus supplement reflects and assumes no issuance, exercise or settlement of stock-based awards under our equity incentive plans.

Unless otherwise stated, all information contained in this prospectus supplement reflects an assumed public offering price of $1.17 per share, which was the last reported sale price of our common shares on the NYSE American on May 10, 2024.

S-3

RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully review the risks and uncertainties described below and under the heading "Risk Factors" in our most recent Annual Report on Form 10-K, as updated by our subsequent quarterly reports on Form 10-Q and other reports and documents that are incorporated by reference into this prospectus supplement, before deciding whether to purchase any of our common shares in this offering. Each of the risk factors could adversely affect our business, results of operations, and financial condition, as well as adversely affect the value of an investment in our common shares, and the occurrence of any of these risks might cause you to lose all or part of your investment. Additional risks not presently known to us or that we currently believe are immaterial may also significantly impair our business operations.

Our management might apply the net proceeds from this offering in ways with which you do not agree and in ways that may impair the value of your investment.

Because we have not designated the amount of net proceeds from this offering to be used for any particular purpose, our management will have broad discretion as to the application of the net proceeds from this offering and could use them for purposes other than those contemplated at the time of the offering. Our management might apply these proceeds in ways with which you do not agree, or in ways that do not improve our financial condition or market value, which could compromise our ability to pursue our growth strategy and adversely affect the market price of our common shares.

You may experience immediate and substantial dilution.

The offering price per share in this offering may exceed the net tangible book value per common share outstanding prior to this offering. Assuming that an aggregate of 34,159,337 of our common shares are sold at a price of $1.17 per share, the last reported sale price of our common shares on the NYSE American on May 10, 2024, for aggregate gross proceeds of approximately $39,966,424, and after deducting commissions and estimated offering expenses payable by us, you would experience immediate dilution of $0.94 per share, representing the difference between our as adjusted net tangible book value per share as of March 31, 2024 after giving effect to this offering and the assumed offering price. The exercise of outstanding stock options, and the vesting and settlement of outstanding restricted stock units, may result in further dilution of your investment. See the section titled "Dilution" below for a more detailed illustration of the dilution you would incur if you purchase shares in this offering. Because the sales of the common shares offered hereby will be made directly into the market or in any other method permitted by law deemed to be an "at the market offering" as defined in Rule 415(a)(4) promulgated under the Securities Act, the prices at which we sell these shares will vary and these variations may be significant. Purchasers of the shares we sell, as well as our existing shareholders, will experience significant dilution if we sell shares at prices significantly below the price at which they invested.

The actual number of shares we will issue under the sales agreement in this offering, at any one time or in total, is uncertain.

Subject to certain limitations in the sales agreement and compliance with applicable law, we have the discretion to deliver a placement notice to B. Riley at any time throughout the term of the offering under this prospectus supplement. The number of shares that are sold by B. Riley after delivering a placement notice will fluctuate based on the market price of our common shares during the sales period and limits we set with B. Riley. Because the price per share of each share sold will fluctuate based on the market price of our common shares during the sales period, it is not possible at this time to predict the number of shares, if any, that will be ultimately sold in this offering.

The common shares offered hereby will be sold in "at the market offerings," and investors who buy shares at different times will likely pay different prices.

Investors who purchase shares in this offering at different times will likely pay different prices, and as result they may experience different levels of dilution and different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices, and numbers of shares sold in this offering. In addition, there is no minimum or maximum sales price for shares to be sold in this offering. Investors may experience a decline in the value of the shares they purchase in this offering as a result of sales made at prices lower than the prices they paid.

S-4

You may experience future dilution as a result of future equity offerings.

To raise additional capital, we may in the future issue additional common shares or other securities convertible into or exchangeable for common shares at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing shareholders. The price per share at which we sell additional common shares, or securities convertible or exchangeable into common shares, in future transactions may be higher or lower than the price per share paid by investors in this offering.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, and the documents incorporated by reference into this prospectus supplement, contain forward-looking statements. These statements are based on our management's current beliefs, expectations and assumptions about future events, conditions and results and on information currently available to us. Discussions containing these forward-looking statements may be found, among other places, in the sections titled "Business," "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" incorporated by reference from our most recent Annual Report on Form 10-K and our most recent subsequent Quarterly Report on Form 10-Q, as well as any amendments thereto, filed with the SEC.

In some cases, you can identify forward-looking statements by terminology such as "aim," "anticipate," "assume," "believe," "contemplate," "continue," "could," "design," "due," "estimate," "expect," "goal," "intend," "may," "objective," "plan," "predict," "positioned," "potential," "seek," "should," "target," "will," "would" or the negative or plural of those terms, and similar expressions intended to identify statements about the future, although not all forward-looking statements contain these words. These forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from the information expressed or implied by these statements.

Any statements in this prospectus supplement, or incorporated herein by reference, about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. These forward-looking statements include statements regarding:

• the potential to receive developmental, regulatory, and commercialization milestone and royalty payments under our Collaboration and License Agreement with F. Hoffmann-La Roche Ltd and Genentech, Inc.;
• our plans to research, develop and commercialize our product candidates;
• the initiation, progress, success, cost and timing of our clinical trials and other product development activities;
• the therapeutic potential of our product candidates, and the indications for which we intend to develop our product candidates;
• our ability to successfully manufacture our product candidates for clinical development and, if approved, for commercialization, and the timing and costs of such manufacture;
• the potential of our cell therapy platform;
• our ability to obtain additional capital to fund our operations;
• our expectations and plans regarding existing and potential future collaborations with third parties such as pharmaceutical and biotechnology companies, government agencies, academic laboratories, and research institutes for the discovery, development, and/or commercialization of novel cell therapy products;
• the size and growth of the potential markets for our product candidates and our ability to serve those markets;
• the potential scope and value of our intellectual property rights; and

S-5

• the effects on our operations of the Israel-Hamas war, other geopolitical conflicts, political and economic instability, public health emergencies and macroeconomic conditions.

You should refer to the "Risk Factors" section in this prospectus supplement and in any free writing prospectus we authorize for use in connection with this offering, and under similar headings in the other documents that are incorporated by reference into this prospectus supplement, for a discussion of important factors that may cause our actual results to differ materially from those expressed or implied by our forward-looking statements. Given these risks, uncertainties and other factors, many of which are beyond our control, we cannot assure you that the forward-looking statements in this prospectus supplement, or incorporated by reference herein, will prove to be accurate, and you should not place undue reliance on these forward-looking statements. Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame, or at all.

Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to revise any forward-looking statements to reflect events or developments occurring after the date of this prospectus supplement, even if new information becomes available in the future.

USE OF PROCEEDS

In this offering, we may issue and sell common shares having aggregate sales proceeds of up to $39,966,424 from time to time. Because there is no minimum offering amount required as a condition to close this offering, the actual total offering amount, commissions and proceeds to us, if any, are not determinable at this time. There can be no assurance that we will sell any shares under or fully utilize the sales agreement with B. Riley as a source of financing.

We will retain broad discretion over the use of the net proceeds from this offering. We currently intend to use the net proceeds from this offering for working capital and general corporate purposes, including research and development and capital expenditures. We may also use a portion of the net proceeds to acquire or invest in businesses and products or product candidates, although we have no current plans, commitments or agreements with respect to any acquisitions as of the date of this prospectus supplement. Pending the use of net proceeds, we plan to invest the net proceeds in short-terminterest-bearinginvestment-grade securities, certificates of deposit or government securities.

DILUTION

Our net tangible book value on March 31, 2024 was approximately $13.8 million, or approximately $0.08 per common share. Net tangible book value per common share is determined by dividing our net tangible book value, which consists of tangible assets less total liabilities, by the number of common shares outstanding on that date. If you purchase shares in this offering, your ownership interest will be diluted immediately to the extent of the difference between the price you pay per common share in this offering and the as adjusted net tangible book value per common share after this offering.

After giving effect to the sale of 34,159,337 common shares in this offering at an assumed offering price of $1.17 per share, the last reported sale price of our common shares on the NYSE American on May 10 , 2024, and after deducting estimated offering commissions and offering expenses payable by us, our as adjusted net tangible book value as of March 31, 2024, would have been approximately $52.3 million, or $0.23 per share. This would represent an immediate increase in the net tangible book value of $0.15 per share to existing shareholders and an immediate dilution of $0.94 per share to investors purchasing our shares in this offering at the assumed public offering price. The following table illustrates this dilution on a per share basis:

Assumed public offering price per share			$	1.17
Net tangible book value per share as of March 31, 2024	$	0.08
Increase in net tangible book value per share attributable to the offering	$	0.15
As adjusted net tangible book value per share as of March 31, 2024, after giving effect to
this offering			$	0.23
Dilution per share to investors purchasing shares in this offering					$	0.94

S-6

The table above assumes for illustrative purposes that an aggregate of 34,159,337 common shares are sold in this offering during the term of the sales agreement with B. Riley at a price of $1.17 per share, the last reported sale price of our common shares on the NYSE American on May 10, 2024, for aggregate gross proceeds of $39,966,424. The shares subject to the sales agreement with B. Riley are being sold from time to time at various prices. An increase of $0.25 per share in the price at which the shares are sold from the assumed public offering price of $1.17 per share shown in the table above, assuming all of our common shares in the aggregate amount of approximately $39,966,424 during the term of the sales agreement with B. Riley is sold at that price, would increase our as adjusted net tangible book value per share after the offering to $0.24 per share and would increase the dilution in net tangible book value per share to new investors in this offering to $1.18 per share, after deducting commissions and estimated aggregate offering expenses payable by us. A decrease of $0.25 per share in the price at which the shares are sold from the assumed public offering price of $1.17 per share shown in the table above, assuming all of our common shares in the aggregate amount of approximately $39,966,424 during the term of the sales agreement with B. Riley is sold at that price, would decrease our as adjusted net tangible book value per share after the offering to $0.23 per share and would decrease the dilution in net tangible book value per share to new investors in this offering to $0.69 per share, after deducting commissions and estimated aggregate offering expenses payable by us. This information is supplied for illustrative purposes only.

The above discussion and table are based on 188,753,536 of our common shares outstanding as of March 31, 2024, and excludes, as of that date, the following:

• 26,387,932 common shares issuable upon the exercise of outstanding stock options with a weighted average exercise price of $1.53 per share awarded under our equity incentive plans or outside of our equity incentive plans pursuant to approval by the independent members of our board of directors in reliance the exception for inducement grants to new employees under the NYSE American Company Guide;
• 501,032 common shares issuable upon vesting and settlement of outstanding restricted stock units under our equity incentive plans; and
• 22,273,132 common shares available for future grant under our 2021 Equity Incentive Plan.

To the extent that any stock options outstanding as of March 31, 2024 have been or may be exercised, restricted stock units outstanding as of March 31, 2024 have or will vest and settle, new stock-based awards are issued under our 2021 Equity Incentive Plan, or we issue additional common shares in the future, including in connection with other capital raising transactions, investors purchasing our shares in this offering may experience further dilution.

PLAN OF DISTRIBUTION

We entered into a sales agreement with B. Riley on March 22, 2024, under which we may issue and sell our common shares from time to time through or to B. Riley acting as sales agent or principal. Sales of our common shares, if any, under this prospectus supplement and the accompanying prospectus may be made by any method that is deemed an "at the market offering" as defined in Rule 415 promulgated under the Securities Act, including ordinary brokers' transactions through the facilities of the NYSE American at market prices or in block transactions or as otherwise agreed between us and B. Riley.

Each time we wish to issue and sell common shares to B. Riley on an agency basis under the sales agreement, we will notify B. Riley of the number or dollar value of shares to be issued, the dates on which such sales are anticipated to be made and any minimum price below which sales may not be made. Once we have so instructed B. Riley, unless B. Riley declines to accept the terms of such notice, B. Riley has agreed to use its commercially reasonable efforts consistent with its normal trading and sales practices to sell such shares up to the amount specified on such terms. The obligations of B. Riley under the sales agreement to sell our common shares are subject to a number of conditions that we must meet.

Settlement for sales of our common shares sold on an agency basis (i) on or prior to May 24, 2024 will occur on the second trading day and (ii) on or after May 28, 2024 will occur on the first trading day, in each case, following the date on which such sales are made (or any such other settlement cycle as may be in effect pursuant to Rule 15c6-1 under the Exchange Act), or on some other date that is agreed upon by us and B. Riley in connection with a particular transaction, in return for payment of the net proceeds to us. Settlement for sales of common shares sold on a principal basis will occur on such settlement cycle as we and B. Riley may agree and as required by applicable law. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

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