The following discussion and analysis of our financial condition and results of operations should be read in conjunction with the financial statements and notes included in Item 8 of this Annual Report on Form 10-K. In addition to historical financial information, the following discussion contains forward-looking statements that reflect our plans, estimates and beliefs. Our actual results could differ materially from those discussed in the forward-looking statements. Factors that could cause or contribute to these differences include those discussed below and elsewhere in this Annual Report, including, but not limited to, those set forth in "Cautionary Note Regarding Forward-Looking Statements" and "Risk Factors."

Overview

We are a preclinical stage biotechnology company pioneering a new class of therapeutics and seeking to develop functional cures for patients with acute and chronic diseases by providing stable and durable levels of therapeutic molecules to patients. We have developed our Shielded Living Therapeutics, or SLTx, platform, which combines advanced cell engineering with cutting-edge innovations in cell differentiation and biocompatible materials, and enables our product candidates to provide a wide range of functions or therapeutic molecules that may be missing or dysfunctional in patients. We are designing our product candidates to be off-the-shelf, durable, controllable and redosable, without requiring modification of the patient's genes or chronic suppression of the patient's immune system.

Since our inception, we have devoted substantially all of our efforts to raising capital, obtaining financing, filing and prosecuting patent applications, organizing and staffing our company and incurring research and development costs related to advancing our biomedical platform. We do not have any products approved for sale and have not generated any revenue from product sales. To date, we have funded our operations primarily with proceeds from sales of common stock and convertible preferred stock, payments received under our collaboration agreement with Lilly and proceeds from borrowings under our credit facilities. Through December 31, 2022, we have received gross proceeds of $144.9 million from the sale of common stock in the IPO, $142.4 million from sales of our convertible preferred stock and net proceeds of $19.8 million through borrowings under our loan and security agreement with Oxford Finance LLC, or the 2020 Credit Facility, partially offset by the $15.0 million repayment of debt from our 2019 Credit Facility. We have also partnered one of our encapsulation technology programs with Lilly. Under the terms of the partnership, we received an upfront payment of $62.5 million and we are eligible to receive additional milestone payments of up to $165.0 million upon achievement of certain regulatory milestones and sales-based milestones of up to $250.0 million for SIG-002. We are also eligible to receive tiered royalty payments in the mid-single digit to low-double digit percentages based on certain sales thresholds. Finally, Lilly is obligated to reimburse us for costs incurred to perform the research and development activities for the first developed product candidate, including costs up to $47.5 million. As of December 31, 2022 and 2021, we had $2.2 million and $0.1 million in accounts receivable and $1.3 million and $0 in unbilled accounts receivable with Lilly, respectively.

We have incurred significant operating losses since our inception. Our ability to generate any product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more of our product candidates. We reported net losses of $43.6 million and $77.3 million for the years ended December 31, 2022 and 2021, respectively. As of December 31, 2022, we had an accumulated deficit of $256.8 million. We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We anticipate that our expenses will increase substantially if and as we:

? continue our current research programs and our preclinical development of

product candidates from our current research programs;

? seek to identify additional research programs and additional product

candidates;

? conduct additional preclinical studies for our product candidates;

? initiate clinical trials for our Mucopolysaccharidosis Type I, or MPS-1,

program, or any other product candidates;




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comply with regulatory requirements established by the U.S. Food and Drug

? Administration, or FDA, the European Medicines Agency, or EMA, and other

comparable foreign regulatory authorities;

? seek marketing approvals for any of our product candidates;

? ultimately establish a sales, marketing, and distribution infrastructure to

commercialize any medicines for which we may obtain marketing approval;

? further develop our SLTx platform;

? hire additional research, development, manufacturing, quality, supply chain and

commercial personnel;

? continue to hire and retain research and clinical personnel;

add operational, financial, corporate development and management information

? systems and legal personnel, including personnel to support our product

development and planned future commercialization efforts;

? expand our facilities;

? acquire or in-license product candidates, intellectual property and

technologies;

scale up manufacturing and supply chain capacity to meet future clinical and

? commercial demand, including scaling up processes for cell culture and

automated encapsulation, and building or expanding our manufacturing

capabilities or capacity, including future manufacturing facilities;

file, prosecute, defend, and enforce our patent claims and other intellectual

property rights, including patent infringement actions brought by third parties

? against us regarding our investigational medicines or actions by us challenging

the patent or intellectual property rights of others, and provide reimbursement

of third-party expenses related to our patent portfolio; and

? operate as a public company.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for one or more of our product candidates. If we obtain regulatory approval for any of our product candidates, we expect to incur significant expenses related to developing our commercialization capability to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, or other capital sources, including collaborations with other companies and other strategic transactions. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed on favorable terms, or at all. If we fail to raise capital or enter into such agreements as, and when, needed, we may have to significantly delay, scale back or discontinue the development and commercialization of one or more of our product candidates.

Because of the numerous risks and uncertainties associated with pharmaceutical product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve or maintain profitability. Even if we are able to generate product sales, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce or terminate our operations.



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Components of Results of Operations

Revenue

To date, we have not generated any revenue from product sales and do not expect to generate any revenue from the sale of products in the near future. Substantially all of our revenue to date has been derived from the collaboration agreement with Lilly, which we entered into in 2018.

If our development efforts for our product candidates are successful and result in regulatory approval or if we enter into license or collaboration agreements with third parties, we may generate revenue in the future from product sales, payments from license or collaboration agreements that we may enter into with third parties, or any combination thereof. We expect that our revenue for the next several years will be derived primarily from our collaboration agreement with Lilly as well as any additional collaborations that we may enter into in the future. We cannot provide assurance as to the timing of future milestone or royalty payments or that we will receive any of these payments at all.

Collaboration Revenue

In April 2018, we entered into a License and Collaboration Agreement with Lilly, or the 2018 Lilly Agreement. Under the 2018 Lilly Agreement, we granted Lilly an exclusive worldwide, royalty-bearing license, including the right to grant sublicenses, to our encapsulation technology applied to islet cells. We are responsible for our own costs and expenses associated with pre-clinical development of a product candidate, and completion of the studies and other criteria required for filing the first IND, up to $47.5 million. Lilly is responsible for filing the first IND, all subsequent clinical development and commercialization, all research, development and commercialization for any subsequent product candidates, as well as reimbursing us for research and development costs required for filing the first IND related to the first developed product candidate that exceed $47.5 million.

We evaluated the 2018 Lilly Agreement under ASC 606 and concluded at the outset that there were two performance obligations under the arrangement: (1) exclusive license to research, develop, manufacture and commercialize licensed products, initial technology transfer, research activities (including pre-IND supply), cell line development and supply and product trademark election, or the Combined Performance Obligation; and (2) requirement to supply Lilly with the licensed product related to Phase 1 clinical trial, or Phase 1 Supply. We determined that the $62.5 million upfront payment represents the entirety of the consideration to be included in the transaction price as of the outset of the arrangement. We allocated $56.6 million of the transaction price to the Combined Performance Obligation and $5.9 million of the transaction price to the Phase 1 Supply at the outset of the arrangement. We recognize revenue for the Combined Performance Obligation as the research and development services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy the Combined Performance Obligation. The transfer of control to the customer occurs over the time period that the research and development services are to be provided by us, and this cost-to-cost method is, in management's judgment, the best measure of progress toward satisfying this performance obligation. We have determined that the Phase 1 Supply will be satisfied at a point in time when the customer obtains control of each unit of product. Therefore, we will recognize revenue as shipments of the Phase 1 Supply are made to Lilly.

We reevaluate the transaction price and our total estimated costs expected to be incurred at the end of each reporting period and as uncertain events, such as changes to the expected timing and cost of certain research, development and manufacturing activities that we are responsible for, are resolved or other changes in circumstances occur, and, if necessary, we will adjust our estimate of the transaction price or our total estimated costs expected to be incurred.

Additional information regarding the 2018 Lilly Agreement can be found in Note 9 to our financial statements in this Annual Report on Form 10-K.



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Operating Expenses

Research and Development Expenses

Research and development expenses consist primarily of costs incurred for our research activities, including our drug discovery efforts and the development of our platform and product candidates. We expense research and development costs as incurred, which include:

employee-related expenses, including salaries, bonuses, benefits, stock-based

? compensation, other related costs for those employees involved in research and

development efforts;

expenses incurred in connection with the preclinical development of our product

? candidates and research programs, including under agreements with third

parties, such as consultants, contractors, and CROs;

the cost of raw materials and developing and scaling our manufacturing process

? and manufacturing product candidates for use in our research and preclinical

studies, including under agreements with third parties, such as consultants,

contractors, and CMOs;

? laboratory supplies and research materials;

? facilities, depreciation, and other expenses, which include direct and

allocated expenses for rent and maintenance of facilities and insurance; and

? payments made under third-party licensing agreements.

We expense research and development costs as incurred. Non-refundable advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed, or when it is no longer expected that the goods will be delivered or the services rendered. Upfront payments under license agreements are expensed upon receipt of the license, and annual maintenance fees under license agreements are expensed in the period in which they are incurred. Milestone payments under license agreements are accrued, with a corresponding expense being recognized, in the period in which the milestone is determined to be probable of achievement and the related amount is reasonably estimable.

Our direct external research and development expenses are tracked on a program-by-program basis, including our early-stage programs, and consist of costs that include fees, reimbursed materials, and other costs paid to consultants, contractors, contract manufacturing organizations or CMOs, and contract research organizations or CROs, in connection with our preclinical and manufacturing activities. Except for personnel expenses related to SIG-002, we do not allocate employee costs, costs associated with our discovery efforts, laboratory supplies and facilities expenses, including depreciation or other indirect costs, to specific product development programs because these costs are deployed across multiple programs and our platform and, as such, are not separately classified. The personnel expenses allocated to SIG-002 do not include stock-based compensation expense.

Product candidates in later stages of clinical development generally have

higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later stage clinical trials. We expect that our research and development expenses will increase substantially in connection with our planned preclinical and clinical development activities in the near term and in the future. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any of our product candidates. The successful development and commercialization of our product candidates is highly uncertain. This is due to the numerous risks and uncertainties associated with product development and commercialization, including the following:

? the timing and progress of preclinical and clinical development activities;




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? the number and scope of preclinical and clinical programs we decide to pursue;

? raising additional funds necessary to complete preclinical and clinical

development of and commercialize our product candidates;

? the progress of the development efforts of parties with whom we may enter into

collaboration arrangements;

? our ability to maintain our current research and development programs and to

establish new ones;

? our ability to establish new licensing or collaboration arrangements;

the successful initiation and completion of clinical trials with safety,

? tolerability and efficacy profiles that are satisfactory to the FDA, or any

comparable foreign regulatory authority;

? the receipt and related terms of regulatory approvals from applicable

regulatory authorities;

? the availability of raw materials for use in the production of our product

candidates;

? our ability to consistently manufacture our product candidates for use in

clinical trials;

? our ability to establish and operate a manufacturing facility, or secure

manufacturing supply through relationships with third parties;

? our ability to obtain and maintain patents, trade secret protection and

regulatory exclusivity, both in the United States and internationally;

? our ability to protect our rights in our intellectual property portfolio;

? the commercialization of our product candidates, if and when approved;

? obtaining and maintaining third-party insurance coverage and adequate

reimbursement;

? the acceptance of our product candidates, if approved, by patients, the medical

community and third-party payors;

? competition with other products; and

? a continued acceptable safety profile of our therapies following approval.

A change in the outcome of any of these variables with respect to the development of any of our product candidates could significantly change the costs and timing associated with the development of these product candidates. We may never succeed in obtaining regulatory approval for any of our product candidates.

General and Administrative Expenses

General and administrative expenses consist primarily of salaries and personnel expenses, including stock-based compensation, for our personnel in executive, legal, finance and accounting, human resources, and other administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees paid for accounting, auditing, consulting, and tax services; insurance costs; travel expenses; and facility costs not otherwise included in research and development expenses.



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We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued research activities and development of our product candidates. We also anticipate that we will incur significantly increased accounting, audit, legal, regulatory, compliance and director and officer insurance costs as well as investor and public relations expenses associated with operating as a public company. Additionally, if and when we believe a regulatory approval of a product candidate appears likely, we anticipate an increase in payroll and other employee-related expenses as a result of our preparation for commercial operations, especially as it relates to the sales and marketing of that product candidate.

Other Income (Expense)

Interest Income

Interest income consists of interest earned on our cash, cash equivalents and marketable securities balances. We expect our interest income will fluctuate based on the timing and ability to raise additional funds as well as the amount of expenditures for our platform development and ongoing business operations.

Interest Expense

Interest expense consists of interest expense on outstanding borrowings under our loan and security agreements as well as amortization of debt discount and deferred financing costs.

Other Income, net

Other income consists primarily of insurance proceeds, sublease income, gain on the disposal of fixed assets and net foreign exchange losses.

Income Taxes

Since our inception, we have not recorded any income tax benefits for the net operating losses we have incurred in each year or for our earned research and development tax credits generated in each period, as we believe, based upon the weight of available evidence, that it is more likely than not that all of our net operating loss, or NOL, carryforwards and tax credit carryforwards will not be realized. We have recorded a full valuation allowance against our net deferred tax assets at each balance sheet date.

Critical Accounting Policies and Significant Judgments and Estimates

Our financial statements are prepared in accordance with generally accepted accounting principles in the United States, or GAAP. The preparation of our financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events, and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

While our significant accounting policies are described in more detail in Note 2 to our financial statements included elsewhere in this Annual Report on Form 10-K. We believe that the following accounting policies are those most critical to the judgments and estimates used in the preparation of our financial statements.

Revenue Recognition

To date, our revenues have consisted primarily of payments received related to the 2018 Lilly Agreement. We follow the provisions of ASC Topic 606, Revenue from Contracts with Customers, or ASC 606, for all contracts with



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customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments.

Under ASC 606, we recognize revenue when our customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that we determine are within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract, determine those that are performance obligations and assess whether each promised good or service is distinct. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, we perform the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the assessment of the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as we satisfy each performance obligation. As part of the accounting for arrangements under ASC 606, we must use significant judgment to determine: a) the performance obligations based on the determination under step (ii) above; b) the transaction price under step (iii) above; and c) the standalone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above. We also use judgment to determine whether milestones or other variable consideration, except for royalties and sales-based milestones, should be included in the transaction price as described below. The transaction price is allocated to each performance obligation based on the relative stand-alone selling price of each performance obligation in the contract, and we recognize revenue based on those amounts when, or as, the performance obligations under the contract are satisfied.

The standalone selling price is the price at which an entity would sell a promised good or service separately to a customer. Management estimates the standalone selling price of each of the identified performance obligations in our customer contracts, maximizing the use of observable inputs. Because we have not sold the same goods or services in our contracts separately to any customers on a standalone basis and there are no similar observable transactions in the marketplace, we estimate the standalone selling price of each performance obligation in our customer arrangements based on our estimate of costs to be incurred to fulfil our obligations associated with the performance, plus a reasonable margin.

In assessing whether a license is distinct from the other promises, we consider relevant facts and circumstances of each arrangement, including the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, we consider whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promises, whether the value of the license is dependent on the unsatisfied promises, whether there are other vendors that could provide the remaining promises, and whether it is separately identifiable from the remaining promises. We determined there were two distinct performance obligations at the outset of the 2018 Lilly Agreement, the Combined Performance Obligation and the Phase 1 Supply performance obligation.

For performance obligations which consist of licenses combined with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. The measure of progress, and the resulting periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the arrangement, which are subject to review by a joint research committee, or JRC. Such a change could have a material impact on the amount of revenue we record in future periods. We concluded that the transfer of control to the customer for the Combined Performance Obligation occurs over the time period that the research and development services are provided by us. We recognize revenue for the Combined



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Performance Obligation as those services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy the Combined Performance Obligation. The cost-to-cost method is, in management's judgement, the best measure of progress towards satisfying the performance condition.

For the Phase 1 Supply performance obligation, which was determined to be a material right, the standalone selling price was estimated using the expected cost-plus margin approach. We determined that the Phase 1 Supply will be satisfied at a point in time when the customer obtains control of each unit of product. Therefore, we will recognize revenue as shipments of the Phase 1 Supply are made to Lilly.

At the inception of each arrangement that includes research, development or regulatory milestone payments, we evaluate whether the milestones are considered likely to be met and estimate the amount to be considered for inclusion in the transaction price using the most-likely-amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. For milestone payments due upon events that are not within the control of us or the licensee, such as regulatory approvals, we are not able to assert that it is likely that the regulatory approval will be granted and that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur until those approvals are received. In making this assessment, we evaluate factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period we reevaluate the probability of achievement of all milestones subject to constraint and, if necessary, adjust our estimate of the overall transaction price of the arrangement. Any such adjustments are recorded on a cumulative catch-up basis, which would affect the amount of revenue and earnings in the period of adjustment. As of December 31, 2022, no milestones under the 2018 Lilly Agreement were included in the transaction price as no milestones had been deemed likely to be achieved or had been achieved.

We reevaluate the transaction price and our total estimated costs expected to be incurred at the end of each reporting period and as uncertain events, such as changes to the expected timing and cost of certain research, development and manufacturing activities that we are responsible for, are resolved or other changes in circumstances occur. If necessary, we will adjust our estimate of the transaction price or our total estimated costs expected to be incurred.

During the year ended December 31, 2022, consistent with the Company's presentation to the JRC, the Company revised its estimate of total costs to complete the activities under the 2018 Lilly Agreement to reflect the Company's experiences to date and the impact this has on its expected future research and development activities to satisfy the Combined Performance Obligation. During the year ended December 31, 2022, there has been an increase to the total estimated costs expected to be incurred of $13.5 million compared to the estimate as of December 31, 2021. The increase in total estimated costs impacted both the Company's estimated transaction price for the 2018 Lilly Agreement, as Lilly is obligated to reimburse the Company if the costs exceed $47.5 million to complete the services, and the Company's input method used to recognize revenue, as this measure compares the Company's cumulative costs incurred to the Company's total estimated costs expected to be incurred. During the year ended December 31, 2022, based on the allocation of total transaction price to each performance obligation using the relative stand-alone selling price of each performance obligation under the 2018 Lilly Agreement, the transaction price for the Combined Performance Obligation increased by $12.7 million and the Phase 1 supply performance obligation increased by $1.3 million.

We determined that our only contract liability under ASC 606 is deferred revenue. Amounts received prior to revenue recognition are recorded as deferred revenue in the balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current portion of deferred revenue in the balance sheets. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion in the balance sheets. Amounts are recorded as accounts receivable and unbilled accounts receivable when our right to consideration is unconditional.



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Accrued Research and Development Expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the financial statements based on facts and circumstances known to us at that time. At each period end, we corroborate the accuracy of these estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include those related to fees paid to:

? Vendors in connection with discovery and preclinical development activities;

? CROs in connection with preclinical studies and testing; and

? CMOs in connection with the process development and scale up activities and the

production of materials.

We record the expense and accrual related to contract research and manufacturing based on our estimates of the services received and efforts expended considering a number of factors, including our knowledge of the progress towards completion of the research, development, and manufacturing activities; invoicing to date under contracts; communication from the CROs, CMOs and other companies of any actual costs incurred during the period that have not yet been invoiced; and the costs included in the contracts and purchase orders. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expense accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low in any particular period. To date, there have not been any material adjustments to our prior estimates of accrued research and development expenses.

Stock-Based Compensation

We measure all stock-based awards granted to employees and directors based on their fair value on the date of the grant using the Black-Scholes option-pricing model for options or the market price of our common stock on the grant date for restricted stock units. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the respective award for the employees and directors.

We use the straight-line method to record the expense of awards with only service-based vesting conditions. We record the expense of awards with performance-based vesting when we conclude that it is probable the performance condition will be achieved. The Black-Scholes option-pricing model uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our common stock options, the risk-free interest rate for a period that approximates the expected term of our common stock options, and our expected dividend yield.

Compensation expense for purchases under the Employee Stock Purchase Plan is recognized based on the fair value of the common stock estimated based on the closing price of our common stock as reported on the date of offering, less the purchase discount percentage provided for in the plan.



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Results of Operations

Comparison of the Years Ended December 31, 2022 and 2021



The following table summarizes our results of operations for the years ended
December 31, 2022 and 2021:

                                            Year Ended
                                          December 31,            Increase
                                        2022          2021       (Decrease)

                                          (in thousands)
Revenue
Collaboration revenue                $   12,944    $    9,599    $     3,345
Operating expenses:
Research and development                 37,631        65,069       (27,438)
General and administrative               18,979        20,166        (1,187)
Total operating expenses                 56,610        85,235       (28,625)
Loss from operations                   (43,666)      (75,636)         31,970
Other income (expense):
Interest income                             946           258            688
Interest expense                        (2,290)       (1,988)          (302)
Other income, net                         1,449            55          1,394
Total other income (expense), net           105       (1,675)          1,780
Net loss                             $ (43,561)    $ (77,311)    $    33,750


Revenue

Revenue was $12.9 million for the year ended December 31, 2022, compared to $9.6 million for the year ended December 31, 2021. The Company recognizes revenue under the 2018 Lilly Agreement based on the input method, and as the costs incurred increased by $2.0 million during the year ended December 31, 2022, income recognized also increased. In addition, as the projected costs to complete certain activities decreased, there was an increase in recognized revenue.

Research and Development Expenses

The following table summarizes our research and development expenses for the years ended December 31, 2022 and 2021:



                                                                Year Ended
                                                              December 31,          Increase
                                                             2022        2021      (Decrease)

                                                              (in thousands)

Direct research and development expenses by program: Diabetes program

$ 10,638    $  8,532    $     2,106
MPS-1 program                                                 4,591       6,324        (1,733)
Platform and other early stage programs                      10,094      29,853       (19,759)

Unallocated expenses Personnel expenses (including stock­based compensation) 9,483 15,822 (6,339) Facility related and other

                                    2,825       4,538        (1,713)
Total research and development expenses                    $ 37,631    $ 65,069    $  (27,438)

Research and development expenses were $37.6 million for the year ended December 31, 2022, compared to $65.1 million for the year ended December 31, 2021. The decrease in research and development expenses was primarily related to decreased ongoing platform and other early-stage programs, MPS-1 program, facility related and other and personnel expenses, which were offset by increases in direct research and development expenses for our diabetes program.



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The decrease in platform and pipeline development, MPS-1 program, personnel expenses, and the increase in the diabetes program expenses is primarily due to our reprioritization of the development of MPS-1, diabetes and platform optimization following the Company's restructuring activities in December 2021. The decrease in facility related and other expenses is primarily due to the sublease of a portion of our facility.

General and Administrative Expenses

General and administrative expenses for the year ended December 31, 2022 were $19.0 million, compared to $20.2 million for the year ended December 31, 2021. General and administrative expenses decreased by $1.2 million as a result of decreased personnel expenses primarily in connection with our restructuring activities that occurred in December 2021.

Other Income (Expense), net

Other income (expense), net, primarily consists of insurance income, interest income, and interest expense. Other income (expense), net, for the year ended December 31, 2022 and 2021 was $0.1 million and ($1.7) million, respectively. The increase was primarily due to increased interest income associated with increased investment in marketable securities, insurance income and the gain on the sale of fixed assets, which was offset by increased interest expense due to higher interest rates on our credit agreement.

Liquidity and Capital Resources

Sources of Liquidity

Since our inception, we have incurred significant operating losses. We have not yet commercialized any of our product candidates and we do not expect to generate revenue from sales of any product candidates for the foreseeable future, if at all. To date, we have funded our operations primarily with proceeds from sales of common stock and convertible preferred stock, payments received under our collaboration agreement with Lilly and proceeds from borrowings under our credit facilities. Through December 31, 2022, we had received net proceeds of $131.8 million from the sale of common stock in the IPO, $141.9 million from the net sales of our convertible preferred stock and net proceeds of $19.8 million through borrowings under our loan and security agreement with Oxford Finance LLC, or the 2020 Credit Facility. We have also partnered one of our encapsulation technology programs with Lilly. Under the terms of the partnership, we received an upfront payment of $62.5 million and we are eligible to receive additional milestone payments of up to $165.0 million upon achievement of certain regulatory milestones and sales-based milestones of up to $250.0 million for SIG-002. We are also eligible to receive tiered royalty payments in the mid-single digit to low-double digit percentages based on certain sales thresholds. Finally, Lilly is obligated to reimburse us for costs incurred to perform the research and development activities for the first developed product candidate that exceed $47.5 million. We are also eligible to receive additional payments upon the achievement of specified regulatory and sales milestones and royalty payments. As of December 31, 2022, we had cash, cash equivalents and marketable securities of $69.6 million.

On April 14, 2022, we entered into an Equity Distribution Agreement with Canaccord Genuity LLC, or Canaccord, pursuant to which we may issue and sell shares of common stock, from time to time, having an aggregate offering price of up to $10.0 million. Sales of common stock through Canaccord may 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. We are not obligated to make any sales of its common stock under the Equity Distribution Agreement. Any sales under the Equity Distribution Agreement will be made pursuant to our registration statement on Form S-3 (File No 333- 264296) , which became effective on April 22, 2022 and the prospectus relating to such offering.



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Cash Flows

The following table summarizes our sources and uses of cash for each of the
periods presented:

                                                                      Year Ended
                                                                    December 31,
                                                                  2022          2021

                                                                    (in thousands)
Net cash used in operating activities                          $ (51,474)    $ (78,405)
Net cash used in investing activities                            (12,081)      (18,060)
Net cash (used in) provided by financing activities               (1,606)         1,554

Net decrease in cash, cash equivalents and restricted cash $ (65,161) $ (94,911)

Operating Activities

During the year ended December 31, 2022, operating activities used $51.5 million of cash, primarily resulting from our net loss of $43.6 million and net cash used in changes in our operating assets and liabilities of $19.3 million, partially offset by non-cash charges of $11.4 million. Net changes in our operating assets and liabilities for the year ended December 31, 2022 consisted primarily of a $9.5 million decrease in deferred revenue, a $4.1 million decrease in lease liabilities, a $2.9 million decrease in accrued expenses and other current liabilities, a $2.1 million increase in accounts receivable, a $1.3 increase in unbilled accounts receivable, and $1.2 million decrease in accounts payable, offset by a decrease in prepaid expenses and other current assets of $1.7 million and a $0.2 million increase in other liabilities. The decrease in deferred revenue was due to recognition of revenue related to our collaboration agreement. The increase in accounts receivable and unbilled accounts receivable was due to work performed related to our collaboration agreement that was either not paid or not invoiced as of the year ended December 31, 2022. The decrease in accounts payable and accrued expenses and other current liabilities was the result of timing of payments for services performed by our vendors. The decrease in lease liabilities was primarily due to payment of rent for our leased property. The increases in prepaid expenses and other current assets were the result of timing of payments for services to be performed in future periods.

During the year ended December 31, 2021, operating activities used $78.4 million of cash, primarily resulting from our net loss of $77.3 million and net cash used in changes in our operating assets and liabilities of $13.4 million, partially offset by non-cash charges of $12.3 million. Net changes in our operating assets and liabilities for the year ended December 31, 2021 consisted primarily of a $9.4 million decrease in deferred revenue, a $4.7 million decrease in lease liabilities and a $1.0 million increase in prepaid expenses and other current assets, partially offset by a $0.9 million increase in accrued expenses and other current liabilities and a $0.7 million increase in accounts payable. The decrease in deferred revenue was due to recognition of revenue related to our collaboration agreement. The decrease in lease liabilities was primarily due to payment of rent for our leased property. The increase in accrued expenses and other current liabilities and accounts payable were primarily due to the timing of vendor invoicing and payments.

Investing Activities

During the year ended December 31, 2022, net cash used in investing activities was $12.1 million and consisted of $42.5 million in purchases of marketable securities, and $0.5 million in purchases of laboratory equipment and furniture and fixtures, offset by $30.8 million in proceeds from maturities of marketable securities and proceeds from the sale of fixed assets of $0.2 million.

During the year ended December 31, 2021, net cash used in investing activities was $18.1 million and consisted of $16.2 million in purchases of marketable securities and $1.8 million in purchases of laboratory equipment and furniture and fixtures.



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Financing Activities

During the year ended December 31, 2022, net cash used in financing activities was $1.6 million, consisting primarily of $1.7 million in repayments of principal associated with our debt facility, offset by $0.1 million of the proceeds from our employee stock purchase plan.

During the year ended December 31, 2021, net cash provided by financing activities was $1.6 million, consisting primarily of the proceeds from the exercise of stock options of $2.2 million, which was partially offset by $0.6 million in the payment of issuance costs associated with our initial public offering in December 2020.

Loan and security agreement

In September 2020, the Company entered into a loan and security agreement, or the 2020 Credit Facility, with Oxford Finance LLC, or Oxford. Effective as of September 2020, the Company paid off in full its borrowings under our prior debt facility using part of the proceeds from the 2020 Credit Facility and accounted for this as a debt extinguishment. The 2020 Credit Facility initially provided for borrowings of up to $20.0 million under one term loan, or the Term A Loan, as well as additional borrowings of up to an aggregate of $5.0 million, under one additional term loan, or the Term B Loan, collectively the "Term Loans". Under the 2020 Credit Facility, the Company borrowed $20.0 million in September 2020. The Company did not elect to borrow the additional $5.0 million under the Term B Loan and the option to borrow under the Term B Loan has expired. Borrowings under the 2020 Credit Facility bear interest at an annual rate equal to greater of 8.40% and the sum of the thirty-day U.S. Dollar LIBOR rate report in the Wall Street Journal plus 8.23%, and are repayable in monthly interest only payments through August 2022 and in equal monthly payments of principal plus accrued interest from September 2022 until the maturity date in August 2025. Upon repayment of the Term Loans, the Company is required to make a final payment to Oxford equal to 3.5% of the original principal amount of the Term Loans funded which will be accrued by charges to interest expense over the term of the loans using the effective-interest method.

Borrowings under the 2020 Credit Facility are collateralized by substantially all of our personal property, other than our intellectual property. There are no financial covenants associated with the 2020 Credit Facility; however, we are subject to certain affirmative and negative covenants to which we will remain subject until maturity. These covenants include limitations on dispositions, mergers or acquisitions; encumbering our intellectual property; incurring indebtedness or liens; paying dividends; making certain investments; and engaging in certain other business transactions. In addition, we are required to, among other things, on an annual basis to deliver Oxford Finance LLC annual audited financial statements. Obligations under the 2020 Credit Facility are subject to acceleration upon the occurrence of specified events of default, including a material adverse change in our business, operations or financial or other condition.

As of December 31, 2022 and 2021, the interest rate applicable to borrowings under the 2020 Credit Facility was 12.4% and 8.40%, respectively. During the year ended December 31, 2022 and 2021 the weighted average effective interest rate on outstanding borrowings was 13.8% and 9.8%.

As of December 31, 2022, we were in compliance with all debt covenants pursuant to the 2020 Credit Facility. We cannot be assured that we will be able to obtain additional covenant waivers or amendments in the future which may have a material adverse effect on our results or operations or liquidity.

Funding requirements

We expect our expenses to increase substantially in connection with our ongoing activities, particularly as we advance the preclinical activities and clinical trials for our product candidates in development. The timing and amount of our operating and capital expenditures will depend largely on:

the costs of continuing to develop our SLTx platform, including the cost of any

? changes to our cells, spheres or manufacturing processes and the costs of any

additional preclinical studies we may conduct;

? the costs of acquiring licenses for the components and engineered cell lines

that will be used with our current and future product candidates;




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the scope, progress, results, and costs of discovery, preclinical development,

? formulation development, and clinical trials for our current and future product

candidates;

the costs of preparing, filing, and prosecuting patent applications,

? maintaining and enforcing our intellectual property and proprietary rights, and

defending intellectual property-related claims;

? the costs, timing, and outcome of regulatory review of any of our product

candidates;

the costs of future activities, including product sales, medical affairs,

? marketing, manufacturing, distribution, coverage and reimbursement for any of

our product candidates for which we receive regulatory approval;

the cost of developing and expanding our manufacturing capabilities and

? advancing these manufacturing capabilities to manufacture product candidates

that are commercially viable;

? our ability to establish and maintain additional collaborations on favorable

terms, if at all;

? the success of any collaborations that we may establish and of our license

agreements;

? the achievement of milestones or occurrence of other developments that trigger

payments under any additional collaboration agreements we obtain; and

? the extent to which we acquire or in-license product candidates, intellectual

property and technologies.

We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements into 2025, giving effect to our decreased external spend relating to our MPS-1 program beginning in the first quarter of 2023. We have based this estimate on assumptions that may change, and we could utilize our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making acquisitions or capital expenditures or declaring dividends. If we raise additional funds through additional collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates, or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce or terminate our research, product development or future commercialization efforts, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

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