GenSight Biologics S A : Notice of Extraordinary General Meeting – EGM January 10, 2024

CONVENING OF THE EXTRAORDINARY GENERAL MEETING

ON JANUARY 10, 2024

GENSIGHT BIOLOGICS

A French Société Anonyme (corporation) with share capital of 1,632,726.83 euros

74, rue du Faubourg Saint Antoine 75012 Paris - France

751 164 757 Paris Trade and Companies Registry

Summary
SUMMARY OF THE COMPANY'S SITUATION	1
AGENDA	18
TEXT OF THE DRAFT RESOLUTIONS	19
REPORT OF THE BOARD OF DIRECTORS TO THE EXTRAORDINARY GENERAL MEETING OF
JANUARY 10, 2024	31
PARTICIPATE IN THE GENERAL MEETING	41
REQUEST FOR ADDITIONAL DOCUMENTS AND INFORMATION	44

SUMMARY OF THE COMPANY'S SITUATION

GenSight Biologics S.A. is a clinical-stage biopharma company focused on developing and commercializing innovative gene therapies for retinal neurodegenerative diseases and central nervous system disorders. GenSight Biologics' pipeline leverages two core technology platforms, the Mitochondrial Targeting Sequence (MTS) and optogenetics, to help preserve or restore vision in patients suffering from blinding retinal diseases. GenSight Biologics' lead product candidate, LUMEVOQ® (GS010; lenadogene nolparvovec), is an investigational compound and has not been registered in any country at this stage; a marketing authorization application is currently under review by the EMA for the treatment of Leber Hereditary Optic Neuropathy (LHON), a rare mitochondrial disease affecting primarily teens and young adults that leads to irreversible blindness. Using its gene therapy-based approach, GenSight Biologics' product candidates are designed to be administered in a single treatment to each eye by intravitreal injection to offer patients a sustainable functional visual recovery. LUMEVOQ® (GS010; lenadogene nolparvovec), is an investigational compound in Phase III prior to the filing of a Market Authorisation Application in Europe, in the United-States and in the United Kingdom, notably.

1. Summary of the situation during the past financial year Consolidated Financial Situation

The Company's operating income reduced by 36.9% to €4.9 million in 2022 from €7.7 million in 2021. This decrease was essentially driven by a single quarter of revenues generated in 2022 by LUMEVOQ® in France through the supply of named patient Temporary Authorizations for Use ("ATU nominative"), compared to a full year of revenues generated in 2021, following manufacturing issues at the Company's partner leading to all available vials being used up in March 2022. These revenues amounted to €2.6 million in 2022 compared to €5.3 million a year earlier. The Company expects to resume supply of AAC (Autorisation d'Accès

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Compassionnel, or Early Access Authorisation, former ATU) in France in Q4 2023 as soon as the product becomes available.

The Company also generated research tax credit (Crédit d'Impôt Recherche or CIR), amounting to €2.2 million in 2022 compared to €2.4 million in 2021. This evolution stems directly from the preparation for commercial launch of LUMEVOQ® which expenses are not eligible to CIR.

Research and development expenses decreased by 15.6% year-on-year amounting to €19.3 million in 2022 compared to €22.9 million in 2021. While Phase III clinical trials of LUMEVOQ®

• RESCUE, REVERSE and REFLECT - are now completed and patients entered long term follow- up, the Company maintains its efforts in Chemistry, Manufacturing and Controls (CMC) activities to ensure manufacturing readiness to commercialize under Good Manufacturing Practices (GMP) and notably the production of validation batches as required for a Marketing Authorisation Application (MAA) of LUMEVOQ® in Europe and in the United-States.

The PIONEER Phase I/II Clinical trial for GS030 continued throughout 2022 showing a good safety profile and encouraging efficacy signals. The Company is now recruiting an extension cohort at the highest dose.

Sales and marketing expenses sharply increased by 45.3% over the period amounting to €8.0 million in 2022 from €5.5 million in 2021 reflecting the ramp up of key strategic marketing and market access activities in preparation for a commercial launch of LUMEVOQ® in Europe. The Company also built its local presence in the main European countries, France, Germany, the United Kingdom, Italy and Spain by setting up local commercial affiliates.

General and administrative expenses significantly reduced by 27.7% year-on-year amounting to €5.4 million in 2022 compared to €7.4 million in 2021. This decrease was mainly driven by a reversal of share-based payment non-cash expenses, due to the cancellation of performance shares plans whose conditions were not met timely due to the manufacturing issues at the Company's partner in the United States. The entirety of plans granted in 2020 and 2021 to management were voided in 2021 and 2022.

This decrease was partially offset by a significant increase in professional fees, mainly legal fees in the context of financing transactions and strategic opportunities conducted in 2022, as well as communication fees related to corporate communication and investor relations efforts in 2022.

The Company's operating loss was stable in 2022 amounting to €27.8 million compared to €28.1 million in 2021. Excluding share-based compensation (IFRS2) non-cash expenses, the adjusted operating loss amounted to €31.2 million in 2022 compared to €23.3 in 2021.

The financial profit in 2022 amounted to €0.2 million compared to a loss of €(0.5) million in 2021. The amount in 2022 was essentially composed of a non-cash financial gain related to the change in derivative financial instrument fair value of the Kreos bond financing, fully repaid in December 2022. This financial gain was offset by interest expenses attached to the

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Kreos bond and the state-guaranteed loan (Prêt Garanti par l'État or PGE) based on the effective interest rate.

The Company also recorded foreign exchange gains and losses primarily driven by the purchase of services denominated in U.S. dollars. The net foreign exchange result in 2022 was a gain of €0.6 million.

The Company's net loss in 2022 amounted to €27.6 million compared to €28.6 million in 2021. The average weighted number of shares increased to 46.3 million in 2022 from 45.2 million in 2021 leading the loss per share to decrease by 5.9% to €(0.60) in 2022 from €(0.63) in 2021. Excluding both share-based compensation (IFRS2) and financial Kreos-related (IFRS9) non- cash expenses, the adjusted net loss amounted to €32.7 million in 2022 compared to €24.0 in 2021.

Net cash flows from operating activities amounted to €(33.8) million in 2022 compared to €(17.1) million a year earlier, primarily as a result of a single quarter of revenues generated by LUMEVOQ® in France through ATUs in 2022, as well as building the commercial infrastructure and preparing for the launch of LUMEVOQ® in Europe.

The change was also derived from a significant increase in working capital, amounting to €4.8 million in 2022 compared to €(3.9) million in 2021. This significant change was due to increased prepaid expenses, mainly in manufacturing activities, and no trade receivables at closing in 2022.

Net cash flows from investment activities amounted to €0.2 million in 2022 compared to €(16) thousand in 2021, mainly driven by the activity of the Company's liquidity contract.

Net cash flows from financing activities amounted to €0.1 million in 2022, reflecting the net proceeds from the convertible note with Heights Capital in December for €10.8 million offset by the amortized repayment of the state-guaranteed loan (Prêt Garanti par l'État or PGE) for €3.6 million and the full repayment of the bond financing from Kreos for €4.2 million, as well as the payment of interest on these debts and related to IFRS16 standard application for €1.9 million, and the repayment of obligation under finance leases for €0.9 million.

In 2021, these financing activities amounted to €23.7 million in 2021, reflecting the net proceeds from the private placement in March for €28.1 million partially offset by the amortized repayment of the state-guaranteed loan (Prêt Garanti par l'État or PGE) and the bond financing from Kreos.

Cash and cash equivalents totaled €10.6 million as of December 31, 2022, compared to €44.3 million as of December 31, 2021. The amounts of expected future cash flows related to the reimbursement of our financial debts were €3.4 million at less than one year and €14.5 million at more than one year.

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Following the withdrawal of its Marketing Authorisation Application with the European Medicines Agency (EMA) in April 2023, the Company has taken measures aimed at significantly reducing its operating cash burn from 2023 onwards, thereby extending its current cash runway through June 2023, while negotiating a limited bridge financing with certain existing and new investors with a view to bridge beyond the results of the validation campaign expected in Q3 2023, which in turn would trigger the €12 million Tranche B of the EIB loan and extend the Company's cash runway to the end of 2023. In parallel, the Company is advancing a number of discussions with possible partners on strategic opportunities, including a merger or acquisition.

Clinical Results and Publications

On January 24, 2022, the Company reported that Leber Hereditary Optical Neuropathy (LHON) subjects treated with LUMEVOQ® continued to experience significantly improved vision four years after a single injection of the gene therapy. The findings come from RESTORE (CLIN06), the long-termfollow-up study to which participants in the RESCUE and REVERSE Phase III pivotal trials were invited.

When RESTORE subjects enrolled in the study, 2 years after the one-time injection, they had already experienced clinically meaningful improvements relative to the lowest point (the "nadir") of their best corrected visual acuity (BCVA): +18.8 ETDRS letters equivalent* in their LUMEVOQ®-treated eyes and +17.3 letters equivalent in their sham-treated eyes. Four years after treatment, the bilateral improvement from nadir was sustained, with LUMEVOQ®-treated eyes achieving a mean improvement against nadir of +22.5 letters equivalent and sham- treated eyes demonstrating a mean improvement of +20.5 letters equivalent.

The impact of such results on patients is demonstrated by increases in the self-reported quality of life (QoL) scores at Year 4 vs. baseline. Mean overall QoL increased by a clinically meaningful magnitude relative to baseline, driven by clinically meaningful increases in the sub-scores corresponding to mental health and the ability to carry out activities autonomously (e.g., role difficulties, dependency, near and far activities, general vision).

On May 19, 2022, the Company announced that the highly-regarded Journal of Neuro- Ophthalmology has published a qualitative study to explore the impact of Leber Hereditary Optic Neuropathy (LHON) on patients and their relatives. The study was featured in a paper published on the journal's website titled, "The Impact of Leber Hereditary Optic Neuropathy on the Quality of Life of Patients and Their Relatives: A Qualitative Study". It is the first of its kind to explore this condition and its impact for patients and relatives in four different countries.

The study determined that the impact of LHON extends beyond vision-related activity limitations, while addressing its psychosocial impact. It concluded that helping patients and their relatives adapt and cope with vision loss is vital. An accurate and timely diagnosis for patients is also crucial to address these issues and also to allow for early intervention.

Participants reported feeling devastated by the diagnosis of LHON after a lengthy and worrisome diagnostic journey. They were also frustrated by the loss of autonomy that affected

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their relatives. Participants described challenges across several domains: physical capabilities, emotional well-being, interpersonal relationships, work and studies, finances, and recreational activities.

Additionally, the study determined that despite residing in different countries, LHON patients and their relatives described similar experiences in the four areas of focus in this study. These areas include (1) experience leading to the point of diagnosis; (2) impact of their condition on various aspects of life; (3) perceptions about treatment; and (4) expectations toward future therapies.

On July 20, 2022, the Company reported that after 5 years of follow-up, Leber Hereditary Optical Neuropathy (LHON) subjects treated with LUMEVOQ® (GS010) continued to experience significantly improved vision as a result of a one-time injection of the gene therapy treatment. Compared to the trend in vision observed among untreated patients, the findings are a significant divergence from the natural outcomes of LHON.

The data from RESTORE (CLIN06), the long-termfollow-up study to which all participants in the RESCUE and REVERSE Phase III pivotal trials were invited, also continue to show that the treatment is well-tolerated over the 5-yearfollow-up period.

5 years' data on efficacy and safety shows substantial durability evidence and is more extensive than what is typically submitted in a data package for a gene therapy.

Responder analyses at Year 5 indicate that improved BCVA was a benefit for a substantial proportion of the study participants. 71.0% of RESTORE subjects achieved Clinically Relevant Recovery (CRR) against nadir 5 years after treatment, and 80.7% of them had on-chart vision (BCVA ≤ 1.6 LogMAR) in one or both eyes.

On November 17, 2022, the Company announced that the highly regarded neurology journal BRAIN has published efficacy and safety findings at 1.5 Year post-treatment in ND4-LHON patients treated with lenadogene nolparvovec (LUMEVOQ®) from the REFLECT Pivotal clinical trial.

The REFLECT results, whose topline findings were announced by the company on June 30, 2021, show statistically significant visual acuity improvement in ND4-LHON patients from baseline in LUMEVOQ® treated eyes, with an additional effect for bilaterally injected patients in comparison with a unilateral treatment. A good safety profile was observed and was comparable in unilaterally and bilaterally treated patients demonstrating the positive outcome of bilateral injections of LUMEVOQ®.

On December 15, 2022, the Company announced the publication of a peer-reviewed article in the journal Ophthalmology and Therapy highlighting updated efficacy results from a pooled analysis of four Phase 3 studies showing an improvement in visual acuity in ND4-LHON patients treated with lenadogene nolparvovec (LUMEVOQ®).

The article, entitled "Indirect Comparison of Lenadogene Nolparvovec Gene Therapy Versus Natural History in Patients with Leber Hereditary Optic Neuropathy Carrying the m.11778G>A MT-ND4 Mutation", incorporates data from the latest Phase 3 trial REFLECT, increasing the number of treated patients from 76 to 174 since the previously published pooled analysis. A

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group of 208 matched patients from natural history studies was used as an external control group.

The inclusion of REFLECT data permits outcomes in bilaterally treated eyes to be compared to those of patients treated unilaterally. When adjusted for covariates, the bilateral intravitreal injection (IVT) data presented in the article showed an improvement of +22.5 ETDRS letters versus natural history, as compared to an improvement of +17.5 ETDRS letters versus natural history for the unilateral IVT. Bilateral IVT also had an on-chart response rate of 79.2% compared to 67.0% for those with the unilateral IVT.

Overall, the patients with LUMEVOQ® showed a clinically significant and sustained improvement in their visual acuity when compared to the natural history patients. Mean improvement versus natural history was +15 ETDRS letters up to 3.9 years after treatment (p<0.01). At 4 years (48 months) after vision loss, the majority of treated eyes were on-chart compared to less than half of natural history eyes (89.6% versus 48.1%) (p<0.01). When adjusted for covariates of interest (gender, age of onset, ethnicity, and duration of follow-up), the estimated mean gain was - 0.43 logMAR (+ 21.5 ETDRS letters equivalent) versus natural history at last observation (p<0.0001). Thus, the treatment effect remained highly clinically significant when controlling for potential confounding factors.

The evolution of natural history eyes showed an absence of recovery throughout the entire follow-up period, with a plateau up to 36 months followed by a slow decline. By contrast, eyes treated with LUMEVOQ® showed a progressive, continuous and sustained improvement between 12 and 52 months after vision loss.

On February 13, 2023, the Company announced favorable safety data and encouraging efficacy signals at 1-yearpost-gene therapy administration for the PIONEER Phase I/II clinical trial evaluating GS030 for the treatment of retinitis pigmentosa (RP) in 9 patients, with a follow-up up to 4 years (n=1).

RP is a genetic blinding disease that affects between 15,000 and 20,000 new patients each year in the US and the EU for which there is currently no treatment. PIONEER is a first-in- human, multi-center,open-label dose escalation clinical trial evaluating the safety and tolerability of GS030, an optogenetic treatment candidate combining an AAV2-based gene therapy (GS030-DP) with the use of light-stimulating goggles (GS030-MD) in patients with end- stage RP. This therapeutic approach is independent of the causal mutation and therefore applicable to potentially all patients suffering from end-stage RP.

Three cohorts of three patients each were administered one of three doses of GS030-DP (5e10 vg; 1.5e11 vg; 5e11 vg) via a single intravitreal injection in their worst affected eye (i.e., the least-seeing eye). A Data Safety Monitoring Board (DSMB) reviewed the safety data of all treated subjects in each cohort and made recommendations before the extension cohort was enrolled. Based on the good safety profile of GS030, the DSMB recommended selecting the highest dose (5e11 vg) for the extension cohort where patients are currently being recruited.

The safety and tolerability results in the first three completed cohorts recorded only mild and moderate (grade 1 and 2) ocular adverse events (AEs) but no severe (grade 3) AEs, with a follow-up up to 4 years (n=1). The most common ocular AEs were mild intraocular

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inflammation responsive to corticosteroid treatment. Intraocular inflammation occurred in 70% of patients and resolved without sequalae in all patients.

The first use of GS030-MD was performed 8 weeks after injection under medical supervision and the light-stimulating goggles were well tolerated. Subjects performed multiple training sessions in parallel to scheduled study visits.

The patients from the highest dose cohort have reached 1-yearpost-gene therapy administration, enabling the assessment of efficacy signals at one year for the 3 cohorts. Encouraging signs of efficacy at 1 year were demonstrated in some patients after GS030 optogenetic treatment with a vision that improved from being barely able to perceive light before treatment to being able to locate and count objects, with the best results at the highest dose.

On March 9, 2023, the Company announced the publication of a peer-reviewed article in the renowned American Journal of Ophthalmology focusing on pooled safety data from the 5 clinical studies with lenadogene nolparvovec (LUMEVOQ®). This analysis constitutes the largest cohort of ND4-LHON patients studied after gene therapy treatment. It confirms the good overall safety profile of the product in terms of systemic and ocular tolerability, humoral and cellular immune response and highlights a comparable safety profile for unilaterally and bilaterally treated patients.

On March 13, 2023, the Company reported topline efficacy and safety results at 3 years post- treatment administration in the REFLECT Phase III clinical trial with LUMEVOQ® (lenadogene nolparvovec). The results show sustained efficacy and favorable safety for bilateral intravitreal injection of the gene therapy with a statistically significant visual acuity improvement from baseline in both treated eyes, showing an additional benefit of a bilateral injection compared to a unilateral injection.

On March 15, 2023, the Company announced that efficacy and safety data from patients with Leber Hereditary Optic Neuropathy carrying the ND4 mutation (ND4-LHON) treated with lenadogene nolparvovec (LUMEVOQ®, GS010) through early access programs (EAP), were presented at the 49th Annual Meeting of the North American Neuro-Ophthalmology Society (NANOS). The data were collected from EAPs across the US, France, Italy, and the UK.

Lenadogene nolparvovec was made available through EAPs in the respective countries based on unsolicited requests from clinicians and patients and authorized for use by local regulations. Between August 2018 and March 2022, 63 ND4-LHON patients received intravitreal injections of lenadogene nolparvovec, with 67 percent of patients receiving injections in both eyes (bilateral treatment), while 33 percent of patients received an injection in one eye (unilateral treatment). Individual data from 45 out of the 63 patients who had passed the one-year post- treatment point and performed their one-year visit were pooled and analyzed.

The data confirmed the efficacy and safety profile of LUMEVOQ® in a real-world setting.

The mean change in best-corrected visual acuity (BCVA) at one-yearpost-treatment in all eyes was an increase of 22.5 ETDRS letters (-0.45 LogMAR) compared to nadir (i.e., the worst visual acuity achieved from baseline to one-year time point). The improvement was better in patients who received bilateral injections with a mean BCVA improvement of 24.5 ETDRS

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letters (-0.49 LogMAR) versus nadir in comparison to 19.5 ETDRS letters (-0.39 LogMAR) for unilaterally treated patients.

Responder analyses demonstrate clinically meaningful improvement in BCVA in a large proportion of patients' eyes. One year after treatment, 64% of eyes showed an improvement of at least 15 ETDRS letters (0.3 LogMAR) from nadir and 60% of eyes achieved clinically relevant recovery (CRR) from nadir.

The safety results obtained in the EAPs were consistent with those observed in the clinical studies, showing a favorable safety profile of lenadogene nolparvovec. Notably, intraocular inflammation events reported in LUMEVOQ®-treated eyes were comparable in frequency, intensity, and location to those observed in the clinical studies.

Manufacturing

On April 7, 2022, the Company announced a delay in the completion of the validation (PPQ) batches for LUMEVOQ®, the Company's gene therapy for the treatment of Leber Hereditary Optic Neuropathy (LHON). The delay is necessary to implement operational adjustments that will prevent the recurrence of issues with the latest PPQ campaign.

The latest campaign, which was initiated after the Company addressed an equipment issue that caused the 2021 campaign to fail, generated drug substance whose viral genome titer fell below the acceptance threshold. Resulting investigations led by external experts have traced the outcome to operational difficulties in specific stages of the downstream process. To prevent the repeat of these issues, the Company is working with its manufacturing partner to implement targeted corrections around enhanced process control and more rigorous supervision inside the manufacturing suites. In addition, the Company has decided to manufacture smaller engineering lots to confirm the robustness of the corrective actions.

On September 19, 2022, the Company announced the successful completion of the first engineering batch incorporating refinements in the manufacturing process of LUMEVOQ®, the Company's gene therapy for Leber Hereditary Optic Neuropathy (LHON). The batch was the first to implement a set of targeted corrective measures around enhanced process control and strengthened on-site supervision that were identified by the Company and its manufacturing partner in the United States in April this year.

The successful engineering run generated drug substance whose viral genome titer achieved the acceptance threshold, thereby confirming that the manufacturing process of LUMEVOQ® is sound at the defined batch size. In addition, the results demonstrate that corrective actions have successfully fixed issues in the filtration steps of the downstream process, resulting in a significantly improved product yield that had not been achieved previously.

On March 7, 2023, the Company provided an update on the manufacturing and commercialization timelines of LUMEVOQ®, the Company's gene therapy for Leber Hereditary Optic Neuropathy (LHON).

Two engineering batches were successfully manufactured as a result of close collaboration between the Engineering team (Manufacturing Sciences and Technology, MSAT) of Brammer

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Bio (a subsidiary of Thermo Fisher Scientific, or TFS), GenSight's manufacturing partner in the US and the Company's own manufacturing experts. Following these engineering batches, a GMP batch (Good Manufacturing Practices, which are the required standards for commercial batches) was scheduled before initiating the production of the validation campaign (3 consecutive GMP batches, or Process Performance Qualification [PPQ] campaign) necessary to complete the European regulatory dossier reviewed by the European Medicines Agency (EMA). This GMP batch was executed under GMP standards by the Manufacturing Operations team at TFS.

Due to the occurrence of an operational issue at TFS in the handling of the downstream process, the batch has been terminated. The precise root cause was investigated in collaboration with TFS before initiating the validation campaign. This root cause was confirmed in April. To prevent the reoccurrence of such an operational issue and secure a successful outcome, GenSight agreed with TFS to jointly involve the MSAT team and GenSight's own experts (including a person-in-plant at all times) real time in the conduct of the validation campaign.

GenSight now expects to initiate the validation campaign early June 2023, with results expected in Q3 2023. The reports from PPQ batches of the validation campaign will allow to resume supply of AAC (Autorisation d'Accès Compassionnel, or Early Access Authorisation, former ATU) in France in Q4 2023.

Regulatory Affairs

On April 14, 2022, the Company announced that the Committee for Advanced Therapies (CAT) of the EMA has granted the Company a six-month extension for submitting its responses to the Day 120 questions in the regulatory review of LUMEVOQ®, GenSight's gene therapy for the treatment of Leber Hereditary Optic Neuropathy (LHON).

On April 20, 2023, the Company announced that the Committee for Advanced Therapies (CAT) of the Committee Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) assessed the data presented during the oral explanation on LUMEVOQ® European regulatory dossier.

As provided by the review procedure and following responses to the D180 questions, an oral explanation was held on April 19. GenSight invited the world renowned LHON experts, Patrick Yu-Wai-Man, MD, PhD (Cambridge University, UK) and José-Alain Sahel, MD (University of Pittsburgh School of Medicine, USA) to share their clinical practice and perspective on LUMEVOQ® data.

Following interactions with the CAT indicating that the data provided thus far would not be sufficient to support a positive opinion of the marketing authorization of LUMEVOQ® by EMA, GenSight decided to withdraw its application ahead of a final opinion by the CAT. This decision enables the Company to rapidly discuss the best possible path forward for LUMEVOQ® with the EMA, aiming at submitting a new application addressing remaining objections as soon as possible, in Europe and other countries. The company is exploring options including generating new clinical data.

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