Rina-S RAINFOL-01: response durability in platinum-resistant ovarian cancer

October 3, 2026: Part C data disclosed

Genmab presented the single-arm Part C expansion of RAINFOL-01 at IGCS. This completed disclosure is distinct from the earlier randomized dose-optimization Part B and from ongoing confirmatory development. Among 109 treated patients with platinum-resistant ovarian cancer, the reported objective response rate was 45.9% and median duration of response was 12.1 months. These results establish activity and motivate further testing; they do not establish superiority over another drug, an overall-survival benefit or a regulatory approval. [1]

FRα targeting and topoisomerase-I delivery

Folate receptor alpha is expressed in many ovarian cancers and can serve as a route for delivering a cytotoxic payload into tumor cells. Rinatabart sesutecan, or rina-S, is an antibody–drug conjugate coupling an FRα-directed antibody to an exatecan-derived topoisomerase-I inhibitor through a cleavable hydrophilic linker. Its drug-to-antibody ratio is approximately eight. Target recognition, intracellular processing and release of active payload are separate determinants of activity; receptor staining alone is not a complete pharmacodynamic model. [1] [2] [3]

The development strategy includes patients across FRα-expression levels, unlike a claim restricted to a high-expression assay-defined population. Apparent activity after mirvetuximab may be relevant to sequencing because the payload and linker differ, but prior exposure does not prove resistance to every component of the earlier ADC. Cross-study comparisons require matching receptor expression, prior therapies and response assessment. The retrieved clinical disclosures do not provide quantitative exposure–response parameters, intact-conjugate clearance or a validated concentration threshold predicting response.

Part B: preserve the 2024 dose-selection dataset

The Phase 1/2 study NCT05579366 randomized 42 ovarian-cancer patients between 100 mg/m² and 120 mg/m² every three weeks: 22 and 20 treated, respectively. Platinum-resistant disease was present in 90.9% and 95.0%. The September 2024 disclosure reported response rates of 18.2% and 50.0%, with median follow-up around 24 weeks and all reported responses at 120 mg/m² ongoing at that snapshot. This was a small dose-finding comparison, not a powered randomized test against standard care. [2] [3]

The higher-dose release lists one complete and eight partial responses using percentages of 5.6% and 44.4%, while also describing 20 treated patients and incomplete response assessments. The efficacy denominator is not fully reconciled in the retrieved disclosure. We retain the reported 50.0% rather than convert it into an invented 10/20. The later Part C response rate belongs to a new expansion population and must not replace these earlier observations or be interpreted as a within-patient change.

Part C population and single-arm interpretation

Part C treated 109 patients at 120 mg/m² every three weeks. Patients had one to three prior systemic lines, with up to four permitted when mirvetuximab was the last treatment. Fifty-three percent had three or four previous lines; all had received bevacizumab and a taxane, 49.5% a PARP inhibitor and 33% mirvetuximab. The number treated is not an independently documented randomized or protocol-evaluable population. There was no concurrent control, so differences in prognosis and post-study treatment remain potential explanations for comparisons with historical cohorts. [1] [4]

The disclosure supplies more than one year of follow-up but no exact analysis cutoff, complete response-review charter, missing-scan rules or estimand. Duration of response conditions on having responded, whereas progression-free survival includes the broader analyzed population. Those endpoints therefore use different risk sets even when shown in the same announcement. A mature-looking median does not resolve the tail of either distribution; censoring patterns and numbers at risk are needed to judge long-duration estimates.

Part C efficacy at the IGCS disclosure

The 45.9% ORR had a 95% confidence interval of 36.3–55.7%; five complete responses were reported. Median DOR was 12.1 months, with a 95% CI of 6.5–15.4, and 51% of responders had responses lasting at least one year. Median PFS was 9.5 months, 95% CI 7.6–11.3. A response-duration percentage is not a one-year PFS rate and is not a fraction of all 109 patients. No overall-survival comparison, hazard ratio versus chemotherapy or multiplicity-controlled superiority test was disclosed. [1]

Safety at 120 mg/m²

Common reported adverse events included nausea 67.9%, fatigue 57.8%, vomiting 36.7%, constipation 26.6%, decreased appetite 23.9% and abdominal pain 18.3%. Anemia and neutropenia were each 57.8%. Platelet-count decrease and thrombocytopenia were each listed at 34.9%; potentially overlapping preferred terms must not be added as independent patients. Approximately one third experienced serious adverse events and 5.5% discontinued because of adverse events. The release did not supply a complete graded table, exact SAE numerator, treatment-related deaths or all dose-interruption counts. [1] [3]

No emerging ocular, neuropathy, ILD or stomatitis signal was highlighted. That statement describes the sponsor’s signal assessment, not a documented zero in every category. Myelosuppression, gastrointestinal tolerability and cumulative dose delivery remain important when evaluating whether response durability translates into sustained treatment benefit. Growth-factor use in the earlier dose cohorts also affects comparisons of neutropenia rates across studies.

Program ownership and execution

Genmab acquired the program with ProfoundBio in 2024 and is the direct developer of rina-S. Its separate epcoritamab collaboration with AbbVie does not make AbbVie the sponsor of these ADC results. The clinical task ahead is reproducible manufacturing, dose management and controlled confirmation in the intended treatment setting. Part C itself provides no asset-specific cash budget or funded enrollment commitment, so none is inferred from Genmab’s size. Completion of this single-arm disclosure does not complete the broader ovarian-cancer development program. [1] [2]

Sources / References

1. Genmab · IGCS Part C results · October 3, 2026
2. Genmab · ESMO Part B · September 15, 2024
3. Genmab · original RAINFOL presentation
4. ClinicalTrials.gov · RAINFOL-01