Genmab's Rina-S Hits 45.9% ORR in Platinum-Resistant Ovarian Cancer

Genmab A/S announced on October 3, 2026 that its investigational antibody-drug conjugate rinatabart sesutecan, or Rina-S, produced a confirmed objective response rate of 45.9% (95% CI: 36.3–55.7) among 109 treated patients with platinum-resistant ovarian cancer in Part C of the Phase 1/2 RAINFOL-01 trial. The company said median duration of response reached 12.1 months (95% CI: 6.5–15.4), with five complete responses. The data were presented in a late-breaking oral session at the IGCS Congress 2026 in Montreal.

Context — why this ovarian cancer readout matters now

Platinum-resistant ovarian cancer is the setting where most approved therapies eventually stop working, and the company framed durability, not just response rate, as the central question. Genmab said the Part C cohort enrolled patients who had received one to three prior lines of therapy, with a carve-out allowing up to four lines for those whose last prior treatment was mirvetuximab. More than half of patients, 53%, had already cycled through three or four prior regimens.

The report gives no prior-period response rate for Rina-S against which to benchmark the 45.9% figure, so the comparison that matters is internal: every patient had prior bevacizumab and taxane exposure, 49.5% had received a PARP inhibitor, and 33% had received mirvetuximab soravtansine. That is a population already exposed to the folate receptor alpha pathway Rina-S targets.

The catalyst chain is regulatory and competitive. Genmab is running four Phase 3 trials in gynecologic cancers, and Part C is the evidence base the company is using to argue the drug works across FRα expression levels. The company said antitumor activity appeared regardless of FRα expression, including in low expressors and non-expressors, and regardless of prior mirvetuximab.

The macro backdrop is secondary here. This is a single-asset clinical readout, and the equity reaction will hinge on how investors weight the Phase 3 program rather than on rate or index levels, which the report does not address.

Data — what the numbers show

The headline efficacy figures are the ORR of 45.9% with five complete responses, a median duration of response of 12.1 months, and a median progression-free survival of 9.5 months (95% CI: 7.6–11.3). The company said 51% of responders were still in response at one year, and that median follow-up exceeded one year.

Metric	Result
Confirmed ORR	45.9% (95% CI: 36.3–55.7)
Complete responses	5
Median DOR	12.1 months (95% CI: 6.5–15.4)
Median PFS	9.5 months (95% CI: 7.6–11.3)
Responders in response at 1 year	51%
Prior mirvetuximab	33%
Prior PARP inhibitor	49.5%
Prior lines 3 or 4	53%

On tolerability, the company reported fatigue in 57.8% of participants and low-grade gastrointestinal events led by nausea at 67.9%, vomiting at 36.7%, constipation at 26.6%, decreased appetite at 23.9%, and abdominal pain at 18.3%. Hematologic events included anemia and neutropenia at 57.8% each, with decreased platelet count and thrombocytopenia at 34.9% each.

Serious adverse events were reported in roughly one-third of participants, and 5.5% discontinued treatment because of a treatment-emergent adverse event. The company said no safety signals emerged for ocular toxicity, peripheral neuropathy, interstitial lung disease, or stomatitis.

The report provides no peer comparison against other agents in this setting, and no market-level data is referenced, so no cross-trial benchmark is available from the disclosed material.

Analysis — what it means for Genmab and the ADC space

The readout matters most for the Phase 3 program. Genmab is running RAINFOL-02 in platinum-resistant ovarian cancer, RAINFOL-03 in recurrent or progressive endometrial cancer, RAINFOL-04 in platinum-sensitive maintenance, and RAINFOL-07 in second-line platinum-sensitive disease. Part C gives those trials their efficacy assumptions and, critically, their safety profile.

The absence of ocular toxicity, peripheral neuropathy, ILD, or stomatitis signals is the commercially relevant detail. Those toxicities are the ones that have complicated other folate receptor alpha and TOPO1-payload ADCs, and their absence in this cohort is what a differentiated tolerability claim rests on. The 5.5% discontinuation rate is the number that supports that argument.

The counter-argument is sample size and design. Part C is a single-arm cohort of 109 patients, not a randomized comparison, and the confidence interval on the 45.9% ORR runs from 36.3% to 55.7%. Single-arm response rates in heavily pretreated ovarian cancer have historically been difficult to replicate in randomized settings, and the Phase 3 readouts are the arbiter.

On positioning, Genmab trades on Nasdaq under GMAB, and the stock's exposure here is to the probability the market assigns to the Phase 3 program. Investors holding the equity are effectively long the entire gynecologic franchise, not just ovarian. The report does not disclose the terms of any partnership or milestone tied to these results.

Outlook — what to watch next

The near-term catalysts are the four Phase 3 readouts. The company lists RAINFOL-02 in platinum-resistant ovarian cancer (NCT06619236), RAINFOL-03 in endometrial cancer (NCT07166094), RAINFOL-04 in platinum-sensitive maintenance (NCT07225270), and RAINFOL-07 in second-line platinum-sensitive disease (NCT07564141), but gives no timelines for any of them.

Beyond ovarian and endometrial, the program includes Phase 2 trials in non-small cell lung cancer (RAINFOL-05; NCT07288177) and advanced gastrointestinal cancers (RAINFOL-09; NCT07539311). Any expansion of the FRα-agnostic efficacy claim into those tumor types would widen the addressable population well beyond gynecologic disease.

The report names no price levels, no analyst targets, and no regulatory filing dates. Investors watching Genmab should treat the next Phase 3 data release as the binary event, since the company has not disclosed interim analysis timing or filing strategy. The safety profile disclosed here is the baseline those trials will be measured against.

Frequently Asked Questions

What does the 45.9% response rate mean for Genmab investors?

It is the efficacy figure the Phase 3 program is built on. Genmab reported a confirmed ORR of 45.9% in 109 platinum-resistant ovarian cancer patients, with a 12.1-month median duration of response. Because Part C is single-arm, the number sets expectations rather than proving superiority. The four Phase 3 trials listed by the company will determine whether the rate holds in randomized settings.

Why did Genmab highlight low FRα expression in these results?

The company said antitumor activity appeared regardless of FRα expression level, including in low expressors and non-expressors. That matters commercially because a therapy that only works in high expressors requires a companion diagnostic and narrows the eligible population. If the claim holds in Phase 3, Rina-S could be used without pre-selecting patients on FRα status, which the report presents as the company's expectation.

What were the most common side effects in the Rina-S trial?

The company reported fatigue in 57.8% of patients and low-grade gastrointestinal events, with nausea at 67.9%, vomiting at 36.7%, and constipation at 26.6%. Hematologic events included anemia and neutropenia at 57.8% each. Serious adverse events occurred in about one-third of participants, and 5.5% discontinued due to a treatment-emergent adverse event. No ocular toxicity, peripheral neuropathy, ILD, or stomatitis signals were observed.

Bottom Line

Genmab's 45.9% response rate and 12.1-month durability in platinum-resistant ovarian cancer now face validation in four ongoing Phase 3 trials.

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