Light Chain Bioscience – Novimmune SA: Long-term Follow-up of NI-1801 in Platinum Resistant Ovarian Cancer Shows Durable Survival Benefit at 24 Months

Updated Phase 1/1b data presented in a Proffered Paper oral presentation at the 2025 European Society of Medical Oncology (ESMO) Congress in Berlin.

GENEVA--(BUSINESS WIRE)--Light Chain Bioscience, a clinical-stage biotechnology company advancing the next generation of bispecific antibodies to treat cancer, today presented updated long-term results from a Phase 1/1b study of NI-1801 as a monotherapy and in combination with pembrolizumab in heavily pretreated Platinum Resistant Ovarian Cancer (PROC) patients that have no approved standard of care treatment. The data were reported in a Poster presentation at European Society of Medical Oncology (ESMO) Congress in Madrid.

NI-1801 is a first-in-class mesothelin x CD47 bispecific antibody that selectively targets the innate immune checkpoint CD47 on mesothelin-expressing cancer cells.

At the data cutoff of September 2026, the Phase 1b study of NI-1801 in combination with pembrolizumab showed an overall survival (OS) rate at 24 months of 40.2% in 21 patients, with a median survival follow-up of 27 months (8 patients alive, 1 lost to follow-up and 3 ongoing on study treatment beyond two years).

A particularly outstanding survival benefit was observed in patients on treatment for ≥8 weeks in the combination cohort, with 7 out of 10 patients (70%) alive after two years. Median OS has not yet been reached in this subpopulation.

In the monotherapy Phase 1 study, NI-1801 showed an OS rate at 24 months of 16% in 21 patients, with a median survival follow-up of 32.4 months and 3 patients alive, 1 lost to follow-up and one patient ongoing on study treatment for almost three years at the data cutoff.

With extended follow-up, NI-1801 remained safe and well tolerated as monotherapy and in combination with pembrolizumab, with no new safety signals identified. Study treatment related adverse events were mostly transient G1 or G2 events, like infusion related reactions in the first and / or second administration. No G3 related adverse events reported with the monotherapy phase II recommended dose (900 mg every two weeks). G3 related adverse events reported with the combination with pembrolizumab were manageable and consistent with pembrolizumab safety profile. No dose limiting toxicities (DLTs) were reported at any of the explored doses in any of the two cohorts (single agent and in combination with pembrolizumab). No patient discontinued this study in relation to a study treatment related adverse event.

Patients in this study had received ≥ 4 prior lines of chemotherapy, representing the most fragile subpopulation of ovarian cancer patients, a subpopulation where neither chemotherapy nor ADCs have shown survival benefit. By comparison, previous studies of standard-of-care chemotherapy in PROC patients who had received at least one prior line reported a median OS of 9 to 12 months. ²

Jose Saro, MD, Chief Medical Officer, Light Chain Bioscience, said: "These 24-month results reinforce the durability of the survival benefit we first reported in October 2025. The sustained overall survival observed with NI-1801 in combination with pembrolizumab, in a chemotherapy-free regimen and in patients who had exhausted multiple prior lines, is encouraging for a population with very limited options. In particular, the extended plateau observed in the survival curve for patients that remained on treatment for more than 8 weeks represents an outstanding benefit."

Kaïssa Ouali MD, presenting investigator, said: "Patients with platinum-resistant ovarian cancer face a poor prognosis and limited treatment options, highlighting the urgent need for more effective therapies. The long-term survival outcomes observed in this study are encouraging and support further investigation of novel immunotherapeutic approaches. By simultaneously targeting CD47 and the PD-1/PD-L1 pathway, this strategy aims to enhance both innate and adaptive anti-tumor immunity, providing a strong biological rationale for durable clinical benefit in this difficult-to-treat population."

Nicolas Fischer, CEO of Light Chain Bioscience, said: "The maturity of the newly presented survival benefit and favorable safety of NI-1801 strengthens the differentiated profile of our CD47-targeting bispecific approach, versus previously evaluated anti-CD47 monoclonal antibodies. We are looking forward to present progress of the ongoing randomized trials in PROC patients who have received 1–3 prior lines of chemotherapy that has now finished enrollment.”

Details of the Presentation
1334P : NI-1801, a mesothelin x CD47 bispecific antibody: long-term survival as monotherapy and in combination with pembrolizumab, in heavily pretreated (≥4 prior lines) mesothelin expressing platinum resistant epithelial ovarian cancer
Presenter: Kaïssa Ouali MD, Gustave Roussy, Villejuif, Ile de France, France
Poster Display Session: Gynaecological cancers, Hall 5, Monday, 26 October 2026, 12:00-12:45 CET

About ovarian cancer
Ovarian cancer accounts for approximately 200,000 deaths worldwide annually.² It is a heterogeneous disease, showing major differences in incidence, tumor behavior, and outcomes across histological subtypes. Treatment options for platinum-resistant recurrence are limited, with no effective therapies that significantly prolong prognosis.

About NI-1801
Light Chain Bioscience's most advanced asset, NI-1801, is a first-in-class bispecific antibody selectively targeting the innate immune checkpoint CD47 on mesothelin-expressing cancer cells, as a potential treatment for ovarian and other mesothelin+ cancers. NI-1801 is being evaluated in a Phase 1 trial in patients with heavily pretreated PROC. NI-1801 is also being evaluated in a Phase 2 randomized trial in PROC patients who have received 1–3 prior chemotherapy.

About Light Chain Bioscience
Light Chain Bioscience, based in Geneva, Switzerland, is a clinical-stage biotechnology company developing next-generation bispecific antibodies for oncology and immune-related diseases. Leveraging its proprietary κλ body platform, Light Chain Bioscience designs fully human IgG bispecifics with potent and selective biological activity. Its lead programs include selective CD47 blockers for solid tumors and CD28-targeted antibodies such as NI-3201, a PD-L1×CD28 bispecific antibody designed to restore anti-tumor immunity. Light Chain Bioscience has more than two decades of expertise in antibody development and has brought seven monoclonal antibodies through to clinical development stage. The company is advancing innovative immunotherapies that engage both innate and adaptive immunity to achieve durable clinical benefit. For more information, visit https://www.lightchainbio.com/

¹RECIST: Response evaluation criteria in solid tumors
²Sho Sato et al., The New Treatment Approaches for Ovarian Cancer. Cancers (Basel). 2024 Jul 15;16(14):2545