to this Report on Form 6-K. Our actual results may differ materially from those contained in or implied by any forward-looking statements. Overview Silence Therapeutics plc (“we”, “us”, &#x201

Condensed consolidated income statement (unaudited)

Condensed consolidated statement of comprehensive income (unaudited)

Condensed consolidated balance sheet (unaudited)

Condensed consolidated statement of changes in equity (unaudited)

Condensed consolidated statement of cash flows (unaudited)

Notes to the financial statements

Three months ended March 31, 2024

1. General information

Silence Therapeutics plc and its subsidiaries (together the Group ) are primarily involved in the discovery, delivery and development of RNA therapeutics. Silence Therapeutics plc (the Company ), a public company limited by shares registered in England and Wales, with company number 02992058, is the Group's ultimate parent company. The Company's registered office is 27 Eastcastle Street, London, W1W 8DH and the principal place of business is 72 Hammersmith Road, London, W14 8TH.

These unaudited condensed consolidated interim financial statements were approved for issue on May 16, 2024.

These unaudited condensed consolidated interim financial statements do not comprise statutory accounts within the meaning of section 434 of the Companies Act 2006. Statutory accounts for the year ended December 31, 2023, were approved by the board of directors on April 8, 2024 and delivered to the Registrar of Companies. The report of the auditors on those accounts was unqualified and did not contain any statement under section 498 of the Companies Act 2006.

The condensed consolidated interim financial statements have not been audited.

Basis of preparation and accounting policies

This unaudited condensed consolidated interim financial report for the three-month reporting period ended March 31, 2024 have been prepared in accordance with International Accounting Standard 34, Interim Financial Reporting as issued by the International Accounting Standards Board ( IASB ).

The interim report does not include all of the notes of the type normally included in an annual financial report. Accordingly, this report is to be read in conjunction with the annual report for the year ended December 31, 2023 which was prepared in accordance with IFRS (International Financial Reporting Standards) as issued by the IASB.

The accounting policies adopted are consistent with those of the previous financial year and corresponding interim reporting periods.

The preparation of these unaudited condensed consolidated interim financial statements requires management to make judgments, estimates and assumptions that affect the application of accounting policies and the reported amounts of assets and liabilities, income and expense. Actual results might differ from these estimates.

In preparing these unaudited condensed consolidated interim financial statements, the significant judgments made by management in applying the Group's accounting policies and the key sources of estimation uncertainty are disclosed in the Critical Accounting Policies, Judgments and Estimates' section beginning on page 21.

The Group has incurred recurring losses since inception, including net losses of 1.9 million for the three months ended March 31, 2024. As of March 31, 2024, the Group had accumulated losses of 305.7 million.

The Group expects to incur operating losses for the foreseeable future as it continues its research and development efforts, seeks to obtain regulatory approval of its product candidates and pursues any future product candidates the Group may develop.

To date, the Group has funded its operations through upfront payments and milestones from collaboration agreements, equity offerings and proceeds from private placements, as well as management of expenses and other financing options to support its continued operations. During 2021, the Group received $40.0 million ( 30.8 million)

of upfront payments in respect of the AstraZeneca plc ( AstraZeneca ) collaboration, $45.0 million from a private placement of American Depositary Shares ( ADSs ) (approximately $42.0 million / 30.8 million, net of expenses) and an approximately $16.0 million ( 10.7 million) upfront payment (net of taxes withheld, based on the exchange rate at the payment date), related to the Hansoh Pharmaceutical Group Company Limited ( Hansoh ) collaboration executed on October 14, 2021. In August 2022, the Group raised additional funds through a registered direct offering with aggregate gross proceeds of $56.5 million (approximately 46.4 million) before deducting $4.1 million (approximately 3.3 million) in placement agent fees and other expenses. In 2023, the Group received a $10.0 million (approximately 7.9 million) milestone from the AstraZeneca collaboration and $4 million (approximately 3.2 million) in milestones from the Hansoh collaboration. In 2023, the Group also raised gross proceeds of approximately $32.2 million (approximately 25.5 million), before deducting 1.0 million in placement agent fees and other expenses from its open market sale agreement. In January 2024, we raised additional proceeds of 15.7 million ($20 million) before deducting 0.5 million ($0.6 million) in placement agent fees and other expenses, from sales of ADSs under our Sales Agreement. On February 5, 2024, the Group announced a private placement of 5,714,286 of the Company's American Depositary Shares ( ADSs ), each representing three ordinary shares, at a price of US $21.00 per ADS, with new and existing institutional and accredited investors (the Private Placement ). The aggregate gross proceeds of the Private Placement was approximately 95.4 million ($120 million) before deducting approximately 6.1 million ($7.7 million) in placement agent fees and other expenses. The financing syndicate included 5AM Ventures, Frazier Life Sciences, Logos Capital, Nextech Invest Ltd (on behalf of one or more funds managed by it), Redmile Group, TCGX and Vivo Capital. As of March 31, 2024, the Group had cash, cash equivalents and U.S. treasury bills of 152.8 million ($192.8 million).

The Group will need to raise additional funding to fund its operation expenses and capital expenditure requirements in relation to its clinical development activities. The Group may seek additional funding through public or private financings, debt financing or collaboration agreements. Specifically, the Group may receive future milestone payments from existing collaboration agreements which will extend the ability to fund operations. In February 2024, the Group announced that it had achieved another $10 million milestone payment from their AstraZeneca Collaboration following the initiation of a Phase 1 Trial. Additional future milestone payments are dependent on achievement of certain development or regulatory objectives that may not occur. The inability to obtain future funding could impact; the Group's financial condition and ability to pursue its business strategies, including being required to delay, reduce or eliminate some of its research and development programs, or being unable to continue operations or unable to continue as a going concern.

Revenue from collaboration agreements for the three months ended March 31, 2024 predominately relates to the research collaboration agreements the Company entered into with Mallinckrodt in July 2019 and AstraZeneca in March 2020.

Revenue for the three months ended March 31, 2024 comprised 12.3 million of research collaboration income (March 31, 2023: 11.2 million) and 0.1 million of royalty income (March 31, 2023: 0.1 million).

Under the Company's collaboration agreement with Mallinckrodt, the Company received an upfront cash payment of 16.4 million ($20.0 million) in 2019 and was eligible to receive specified development, regulatory and commercial milestone payments. No milestone payments under this agreement were achieved during the three months ended March 31, 2024 (three months ended March 31, 2023: nil). In addition to the upfront and potential milestone payments, Mallinckrodt agreed to fund some of the Company's research personnel and preclinical development costs. The Company recognized the upfront payment, milestone payments, payments for personnel costs and other research funding payments over time, in accordance with IFRS 15 para 35 c).

In March 2023, the Company reacquired exclusive worldwide rights to two preclinical siRNA assets under its Mallinckrodt collaboration, which resulted in a modification of the agreement. No additional performance obligations were identified as a result of the modification as there were no additional goods or services to be provided by the Company and the modification resulted in the partially satisfied performance obligations relating to the two reacquired targets becoming fully satisfied as the Company was no longer obligated to develop these targets. SLN501, the C3 targeting program, remained under the original collaboration agreement. The Company accounted for the modification as if it were part of the existing contract as the remaining services to be delivered form part of a single performance obligation that is partially satisfied at the date of contract modification. The effect of the contract modification was that the consideration originally received for the two preclinical siRNA assets was reallocated to SLN501. The Company recognized the effect of the contract modification on the measure of progress towards complete satisfaction of the SLN501 performance obligation, and recognized an adjustment to revenue at the date of the contract modification on a cumulative catch-up basis. The Company recognized 8.0 million on the contract modification date in the first quarter of 2023. In relation to the reacquired targets, the two preclinical siRNA assets were recognized at fair value. The fair value of those assets has been determined to be nil. Under the modification, the Company agreed to pay future success-based milestones and low single digit royalties on net sales if the projects advance. The Company will recognize these variable success-based milestones as an intangible asset at cost when triggered. Any royalties payable will be expensed in cost of sales.

In March 2024, Mallinckrodt notified us that they will not pursue further development of SLN501 following the completion of the phase 1 clinical trial. This will conclude all required development activities and commitments under the collaboration agreement. During the three months ended March 31, 2024, the Company recognized the remaining 0.5 million in revenue under this agreement (three months ended March 31, 2023: 8.9 million).

Under the Company's collaboration agreement with AstraZeneca, the Company received an upfront cash payment of 17.1 million ($20.0 million) in 2020 with a further amount of 30.8 million ($40.0 million) received in May 2021. The Company is also eligible to receive specified development and commercial milestone payments as well as tiered royalties on net sales, if any. The Company recognizes the upfront payment and milestone payments over time, in

accordance with IFRS 15 para 35 c). During the three months ended March 31, 2024, the Company achieved a milestone payment of approximately 7.9 million ($10.0 million) (three months ended March 31, 2023: nil). In March 2024, we completed our obligations for the second product candidate under our AstraZeneca collaboration. As a result, the remaining revenue of 4.1 million associated with the target was recognized. During the three months ended March 31, 2024, the Company recognized a total of 11.6 million in revenue under this agreement (three months ended March 31, 2023: 2.5 million).

The Company entered into a collaboration agreement with Hansoh on October 14, 2021. The Company received an upfront cash payment of approximately $16.0 million ( 10.7 million, net of taxes based on the exchange rate at the payment date) in December 2021. The Company is eligible to receive development, regulatory and commercial milestones as well as royalties on Hansoh net product sales. During the three months ended March 31, 2024, the Company achieved no milestone payments (three months ended March 31, 2023: nil). The Company recognizes the upfront payment and milestone payments over time, in accordance with IFRS 15 para 35 c). During the three months ended March 31, 2024, the Company recognized a total of 0.2 million in revenue under this agreement (three months ended March 31, 2023: reduction of 0.2 million).

In December 2018, the Company entered into a settlement and license agreement with Alnylam Pharmaceuticals Inc. ( Alnylam ) pursuant to which the Company settled outstanding patent litigation with Alnylam related to its RNAi product ONPATTRO. As part of the settlement, the Company licenses specified patents to Alnylam, and Alnylam pays the Company a tiered royalty of up to one percent of net sales of ONPATTRO in the European Union. The Company was eligible to receive these royalties through December 2023. The Company invoices Alnylam quarterly in arrears based on sales data for that quarter as reported to the Company by Alnylam. Royalty revenue is recognized based on the level of sales when the related sales occur. During the three months ended March 31, 2024, the Company recognized a total of 0.1 million in royalty income from Alnylam (three months ended March 31, 2023: 0.1 million).

4. Segment reporting

In 2024, the Group operated in the specific technology field of RNA therapeutics.

The Group has identified the Chief Executive Officer as the chief operating decision maker ( CODM ). For the three months ended March 31, 2024 and 2023, the CODM determined that the Group had one business segment, the development of RNAi-based medicines. This is consistent with reporting to senior management. The information used internally by the CODM is the same as that disclosed in the financial statements.

An analysis of the Group's assets and revenues by location is shown below:

5. Loss per ordinary share (basic and diluted)

The calculation of the loss per ordinary share is based on the loss for the three months ended March 31, 2024 and on the weighted average number of ordinary shares in issue during the three months ended March 31, 2024 of 131,881,115 (three months ended March 31, 2023: 107,941,744).

The options outstanding at March 31, 2024 and 2023 are considered to be anti-dilutive as the Group is loss-making.

7. Contract liabilities

Contract liabilities comprise entirely deferred revenue in respect of the Mallinckrodt, AstraZeneca and Hansoh research collaborations. The current contract liabilities represent the amount of estimated revenue to be reported in the next twelve months related to amounts invoiced to our partners. Current and non-current contract liabilities include future revenue from collaborations, recharged expenses, upfront payments, and milestones achieved to March 31, 2024.

An additional 1.7 million current tax asset was recognized in respect of research and development tax credits in the three months ended March 31, 2024 (three months ended March 31, 2023: 2.7 million). In addition to this we have also recognized 0.3 million of income from the RDEC scheme in the income statement within research and

development costs for the three months ended March 31, 2024. The Company had a foreign tax expense of 0.2 million for the three months ended March 31, 2024 (three months ended March 31, 2023: 0.2 million).

The current tax asset at March 31, 2024 was 10.7 million, comprised of 2.0 million in respect of research and development activity for the three months ended March 31, 2024 and 8.7 million in respect of the year ended December 31, 2023.

The Group has only one class of shares. All ordinary shares have equal voting rights and rank pari passu for the distribution of dividends.

On October 15, 2021, we entered into an Open Market Sale Agreement (the Sales Agreement ), with Jefferies LLC ( Jefferies ), under which Jefferies, as our exclusive agent, at our discretion and at such times that we may determine from time to time, may sell over a three-year period from the execution of the Sales Agreement up to a maximum of

$100.0 million of ADSs. Under the terms of the Sales Agreement, Jefferies may sell the ADSs at market prices by any method that is deemed to be an at the market offering as defined in Rule 415 under the Securities Act of 1933, as amended. The ADSs offered under the Sales Agreement are being offered pursuant to a registration statement on Form F-3 that became effective on October 22, 2021. We may offer and sell up to $300.0 million of our shares, represented by ADSs, from time to time in one or more offerings. During the year ended December 31, 2023, we sold 3.4 million ADSs for net proceeds of approximately $32.2 million (approximately 25.5 million), before deducting 1.0 million in placement agent fees and other expenses. During the three months ended March 31, 2024, we sold 1.1 million ADSs for net proceeds of approximately 15.7 million ($20 million), before deducting 0.5 million ($0.6 million) in placement agent fees and other expenses. As of March 31, 2024, approximately $47 million of ADSs remained available under the Sales Agreement.

On February 5, 2024, the Group announced a private placement of 5,714,286 of the Company's American Depositary Shares ( ADSs ), each representing three ordinary shares, at a price of US $21.00 per ADS, with new and existing institutional and accredited investors (the Private Placement ). The aggregate gross proceeds of the Private Placement was approximately 95.4 million ($120 million) before deducting approximately 6.1 million ($7.7 million) in placement agent fees and other expenses. The financing syndicate included 5AM Ventures, Frazier Life Sciences, Logos Capital, Nextech Invest Ltd (on behalf of one or more funds managed by it), Redmile Group, TCGX and Vivo Capital.

Details of the ordinary shares issued by the Company during the three months ended March 31, 2024 are as follows:

10. Related party transactions

There were no related party transactions between the Company and its directors, executive officers, or holders of more than 10% of its outstanding share capital and their affiliates, in the three ended March 31, 2024.

11. Subsequent Events

MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

You should read the following discussion and analysis of financial condition and operating results together with our unaudited financial statements as of and for the three months ended March 31, 2024 and the related notes to those unaudited condensed consolidated financial statements included as Exhibit 99.1 to this Report on Form 6-K, as well as our audited consolidated financial statements and related notes as disclosed in our Annual Report on Form 20-F for the year ended December 31, 2023 filed with the Securities and Exchange Commission, or the SEC, on March 13, 2024.

The statements in this discussion with respect to our plans and strategy for our business, including expectations regarding our future liquidity and capital resources and other non-historical statements, are forward-looking statements. These forward-looking statements are subject to numerous risks and uncertainties, including the risks and uncertainties described in Exhibit 99.1 to this Report on Form 6-K. Our actual results may differ materially from those contained in or implied by any forward-looking statements.

Silence Therapeutics plc ( we , us , our , the Company or Silence ) is a biotechnology company focused on discovering and developing novel molecules incorporating short interfering ribonucleic acid, or siRNA, to inhibit the expression of specific target genes thought to play a role in the pathology of diseases with significant unmet medical need. Our siRNA molecules are designed to harness the body's natural mechanism of RNA interference, or RNAi, by specifically binding to and degrading messenger RNA, or mRNA, molecules that encode specific targeted disease-associated proteins in a cell. By degrading the message that encodes the disease-associated protein, the production of that protein is reduced, and its level of activity is lowered. In the field of RNAi therapeutics, this reduction of disease-associated protein production and activity is referred to as gene silencing. Our proprietary mRNAi GOLD (GalNAc Oligonucleotide Discovery) platform consists of precision engineered product candidates designed to accurately target and silence' specific disease-associated genes in the liver. Using our mRNAi GOLD platform, we have generated siRNA product candidates both for our internal development pipeline as well as for out-licensed programs with third-party collaborators. Our wholly owned pipeline is currently focused in three therapeutic areas of high unmet need: cardiovascular disease, hematology and rare diseases.

Zerlasiran (SLN360) is our wholly owned siRNA designed to lower the body's production of apolipoprotein(a), a key component of lipoprotein(a), or Lp(a), that has been associated with an increased risk of cardiovascular events. Elevated Lp(a) is a genetically determined cardiovascular risk factor affecting up to 20% of the world's population and is associated with a high risk of heart attack, stroke and aortic stenosis. There are currently no approved medicines that selectively lower Lp(a). In February 2022, we reported positive results from the single-ascending dose portion of the APOLLO phase 1 program evaluating zerlasiran in 32 healthy adults with Lp(a) levels at or over 150 nmol/L. In the single dose trial, participants in the top two zerlasiran single dose groups (300 mg and 600 mg) were observed to have experienced up to a 96% and 98% median reduction in Lp(a) levels, respectively, and median reductions of up to 71% and 81% from baseline persisted at 150 days. Further analysis showed median time-averaged Lp(a) reductions over 150 days exceeded 80% in the zerlasiran 300 mg and 600 mg dose groups. At day 365, some participants still exhibited substantial knockdown of Lp(a) to approximately 50% of baseline. Zerlasiran was well tolerated with no serious safety concerns reported. In November 2023, we reported positive topline results from the multiple dose portion of the APOLLO program in 36 adults with baseline Lp(a) levels at or over 150 nmol/L and stable atherosclerotic cardiovascular disease (ASCVD). In the multiple dose trial, zerlasiran (200 mg, 300 mg and 450 mg) was administered twice subcutaneously at two different dosing intervals. Data demonstrated a significant reduction from baseline in Lp(a) of up to 99% at 90 days following injection of repeated doses. Lp(a) levels remained approximately 90% lower than baseline at 201 days (end of treatment period) at the two highest doses. A dose dependent reduction in low-density lipoprotein cholesterol (LDL cholesterol) and apolipoprotein B (ApoB) was also observed. Zerlasiran was well tolerated; no clinically important safety concerns were identified. Zerlasiran is currently being evaluated in the ALPACAR-360 phase 2 study in patients with Lp(a) levels at or over 125 nmol/L at high risk of ASCVD events. In March 2024, we announced positive topline 36-week data which showed the phase 2 study met its primary endpoint and demonstrated statistically significant reductions in Lp(a) to week 36. The 60-week study is ongoing and secondary endpoints, including change in Lp(a) from baseline to 48 weeks (end of treatment period), 60 weeks (end of study) and potential effects on other lipids/lipoproteins, will be evaluated. We expect to report topline 48-week data in the second quarter of 2024. We are continuing to prepare and finalize development plans for the zerlasiran phase 3 program. In addition, we are engaged in global partnership discussions for phase 3 development and potential future commercialization.

Divesiran (SLN124) is our wholly owned siRNA designed to inhibit TMPRSS6 expression in the liver to raise hepcidin, a peptide hormone that is the master regulator of systemic iron balance. Divesiran has shown preclinical potential in several hematological disorders. Furthermore, divesiran has demonstrated proof of mechanism in the GEMINI phase 1 trial in healthy volunteers completed in May 2021. In the GEMINI study, divesiran was observed to increase average hepcidin approximately four-fold and reduce serum iron by approximately 50% after a single dose with effects persisting for at least two months. Data were presented at the American Society of Hematology (ASH) 2021 Annual Meeting and published in the American Journal of Hematology in July 2023. Divesiran is currently being studied in the SANRECO phase 1/2 trial in patients with polycythemia vera (PV). Divesiran has FDA Fast Track and orphan disease designations for PV. We plan to report data from the phase 1 portion of the study in the first half of 2024.

The potential of our mRNAi GOLD platform has been validated through ongoing research and development collaborations with leading pharmaceutical companies, such as AstraZeneca and Hansoh. These collaborations collectively represent up to 13 pipeline programs and approximately $5 billion in potential milestones plus royalties.

We believe the potential for our mRNAi GOLD platform to address disease-associated genes in the liver is substantial. Only around one percent of the approximately 14,000 liver expressed genes have been targeted by publicly known siRNAs. Once in the clinic, early-stage GalNAC-conjugated RNAi programs have shown a much greater likelihood of advancement from the current phase of development compared to the pharmaceutical industry average. We aim to maximize our mRNAi GOLD platform by advancing both our proprietary and partnered pipelines.

First Quarter 2024 and Recent Business Highlights

mRNAi GOLD Proprietary Program Updates

Zerlasiran (cardiovascular disease)

-Announced positive topline 36-week data from the ongoing ALPACAR-360 phase 2 study in subjects with a median baseline Lp(a) of approximately 215 nmol/L at high risk of ASCVD events. Zerlasiran was administered at 300 mg subcutaneously every 16 or 24 weeks and 450 mg every 24 weeks.

oStudy demonstrated highly significant reductions in Lp(a) compared with placebo to week 36 (primary endpoint)

oMedian percentage reduction in Lp(a) of 90% or greater were observed for both doses at week 36

oNo new safety concerns were identified

oThe 60-week study is ongoing and secondary endpoints, including change in Lp(a) from baseline to 48 weeks (end of treatment period), 60 weeks (end of study) and potential effects on other lipids/lipoproteins, will be evaluated.

-In April 2024, additional results from the APOLLO phase 1 study of zerlasiran in subjects with baseline Lp(a) at or over 150 nmol/L were published in the Journal of the American Medical Association (JAMA). Published findings demonstrated zerlasiran was well-tolerated and significantly reduced Lp(a) after single and multiple dosing. Results from the single ascending dose portion of the trial were previously published in the April 2022 issue of JAMA.

Divesiran (hematological disorders)

-Advanced enrollment into the phase 1 portion of the SANRECO phase 1/2 study in polycythemia vera ( PV ) patients and remain on-track to report phase 1 data by the end of June 2024.

mRNAi GOLD Partnered Program Updates

-In February 2024, we achieved a $10 million milestone payment from AstraZeneca following the initiation of a phase 1 trial of the first product candidate under our collaboration.

-In March 2024, Mallinckrodt notified us that they will not pursue further development of SLN501 following the completion of the phase 1 clinical trial. This will conclude all activities and commitments under the collaboration agreement.

Collaboration Agreement with AstraZeneca

In March 2020, we entered into a collaboration agreement with AstraZeneca to discover, develop and commercialize siRNA therapeutics for the treatment of cardiovascular, renal, metabolic and respiratory diseases. Under this agreement, AstraZeneca made an upfront cash payment to us of $20.0 million in May 2020. AstraZeneca made an additional unconditional cash payment to us of $40.0 million which was received in May 2021. In March 2020, an affiliate of AstraZeneca also subscribed for 4,276,580 new ordinary shares for an aggregate subscription price of $20.0 million.

The collaboration covers five targets initially, with AstraZeneca having the option to extend the collaboration to a further five targets. AstraZeneca has agreed to pay us $10.0 million upon the exercise of each option to collaborate on an additional target. In May 2023, AstraZeneca nominated the first product candidate under our collaboration, triggering a $10 million option fee to us to advance development on an undisclosed program. In February 2024, AstraZeneca initiated a phase 1 study for this undisclosed program which triggered another $10 million milestone payment to us. In March 2024, we completed our obligations for the second product candidate under our AstraZeneca collaboration. For each target selected, we will be eligible to receive up to $140.0 million in potential milestone payments upon the achievement of milestones relating to the initiation of specified clinical trials, the acceptance of specified regulatory filings and the first commercial sale in specified jurisdictions. For each target selected, we will also be eligible to receive up to $250.0 million in potential commercial milestone payments, upon the achievement of specified annual net sales levels, as well as tiered royalties as a percentage of net sales ranging from the high single digits to the low double digits.

Collaboration Agreement with Mallinckrodt

In July 2019, we entered into a collaboration agreement with Mallinckrodt to develop and commercialize RNAi drug targets designed to silence the complement cascade in complement-mediated disorders. In connection with the execution of this agreement, Mallinckrodt made an upfront cash payment to us of $20.0 million (equivalent to 16.4 million as of the payment date). Under a separate subscription agreement, Cache Holdings Limited, a wholly owned subsidiary of Mallinckrodt, concurrently subscribed for 5,062,167 new ordinary shares for an aggregate subscription price of $5.0 million (equivalent to 4.0 million as of the payment date). Under the agreement, we granted Mallinckrodt an exclusive worldwide license to our C3 targeting program, SLN501, with options to license two additional undisclosed complement-mediated disease targets from us. In July 2020, Mallinckrodt exercised options on the two additional complement targets.

In March 2023, we reacquired exclusive worldwide rights from Mallinckrodt to the two undisclosed preclinical complement targets. Under the terms of the modified agreement, we did not make any upfront payment to get the two assets back and will potentially pay future success-based milestones and low single digit royalties on net sales if the projects advance. SLN501, the C3 targeting program, remained under the original collaboration agreement. In March 2024, Mallinckrodt notified us that they will not pursue further development of SLN501 following the completion of the phase 1 clinical trial. This will conclude all required development activities and commitments under the collaboration agreement.

Collaboration Agreement with Hansoh

On October 15, 2021, we announced a collaboration agreement with Hansoh, one of the leading biopharmaceutical companies in China, to develop siRNAs for three undisclosed targets leveraging our proprietary mRNAi GOLD platform. Under the terms of the agreement, we retain exclusive rights to the first two targets in all territories except the China Region (Greater China, Hong Kong, Macau and Taiwan). Hansoh has the exclusive option to license rights to those two targets in the China Region following the completion of phase 1 studies. We will be responsible for all activities up to option exercise and will retain responsibility for development outside the China region post phase 1 studies. Hansoh will also have the exclusive option to license global rights to a third target at the point of IND filing. Hansoh will be responsible for all development activities post option exercise for the third target. Hansoh made a $16 million upfront payment to us in December 2021. We achieved our first $2 million research milestone payment in the Hansoh collaboration in April 2022. In 2023, we achieved two additional preclinical milestones and received $4 million from the collaboration. We are eligible to receive up to $1.3 billion

in additional development, regulatory and commercial milestones. We will also receive royalties tiered from low double-digit to mid-teens on Hansoh net product sales.

Financial Operations Overview

We do not have any approved products. Accordingly, we have not generated any revenue from product sales, and we do not expect to generate any revenue from the sale of any products unless and until we obtain regulatory approvals for, and commercialize any of, our product candidates. In the future, we will seek to generate revenue primarily from product sales and, potentially, regional or global strategic collaborations with third parties.

Under the Company's collaboration agreement with Mallinckrodt, the Company received an upfront cash payment of 16.4 million ($20.0 million) in 2019 and was eligible to receive specified development, regulatory and commercial milestone payments. The Company recognized the upfront payment, milestone payments, payments for personnel costs and other research funding payments over time, in accordance with IFRS 15 para 35 c).

In March 2023, the Company reacquired exclusive worldwide rights to two preclinical siRNA assets under its Mallinckrodt collaboration, which resulted in a modification of the agreement. No additional performance obligations were identified as a result of the modification as there were no additional goods or services to be provided by the Company and the modification resulted in the partially satisfied performance obligations relating to the two reacquired targets becoming fully satisfied as the Company was no longer obligated to develop these targets. SLN501, the C3 targeting program, remained under the original collaboration agreement. The Company accounted for the modification as if it were part of the existing contract as the remaining services to be delivered form part of a single performance obligation that is partially satisfied at the date of contract modification. The effect of the contract modification was that the consideration originally received for the two preclinical siRNA assets was reallocated to SLN501. The Company has recognized the effect of the contract modification on the measure of progress towards complete satisfaction of the SLN501 performance obligation, and recognized an adjustment to revenue at the date of the contract modification on a cumulative catch-up basis. The Company recognized 8.0 million on the contract modification date. In relation to the reacquired targets, the two preclinical siRNA assets were recognized at fair value. The fair value of those assets has been determined to be nil. Under the modification, the Company agreed to pay future success-based milestones and low single digit royalties on net sales if the projects advance. The Company will recognize these variable success-based milestones as an intangible asset at cost when triggered. Any royalties payable will be expensed in cost of sales.

In March 2024, Mallinckrodt notified us that they will not pursue further development of SLN501 following the completion of the phase 1 clinical trial. This will conclude all required development activities and commitments under the collaboration agreement. During the three months ended March 31, 2024, the Company recognized the remaining 0.5 million in revenue under this agreement (three months ended March 31, 2023: 8.9 million).