Genmab's Rina-S Shows Promise in Advanced Endometrial Cancer, Challenging AbbVie's Elahere

Genmab has released encouraging early data on rinatabart sesutecan (Rina-S), its folate receptor alpha (FRα)-directed antibody-drug conjugate (ADC), in advanced endometrial cancer. The results, which surpassed analyst expectations, are fueling the company's push into phase 3 trials and setting the stage for potential competition with AbbVie's Elahere.

Impressive Response Rates in Phase 1/2 Trial

In data to be presented at the upcoming American Society of Clinical Oncology (ASCO) Annual Meeting, Genmab reported unconfirmed response rates of 50% and 45.5% in the lower and higher dose cohorts, respectively. The trial included patients who had received one to eight lines of prior therapies.

Notably, two complete responses were observed in the lower dose cohort. Approximately 80% of the responses were ongoing in both cohorts at the time of data cutoff, indicating promising durability.

Dr. Tahamtan Ahmadi, Chief Medical Officer at Genmab, contextualized these results: "Historically, the second-line has been an indication where the response rate to chemotherapies are maybe in the 10% to 15% range. We feel very comfortable that the data that is going to be presented in the very near future and publicly available will underscore the point that this is really a best-in-class profile from an efficacy point of view as well as from a durability point of view."

Safety Profile and Market Positioning

The safety profile of Rina-S appears favorable, with Genmab reporting no ocular toxicity, neuropathy, or interstitial lung disease – side effects that have been associated with other ADCs in this class.

Genmab sees endometrial cancer as a key proving ground for Rina-S, aiming to demonstrate efficacy across a broad spectrum of folate receptor alpha expression. This approach forms part of Genmab's strategy to position Rina-S as an improvement over AbbVie's Elahere, an approved ADC targeting the same receptor.

Legal Challenges and Market Potential

The promising data comes amid legal challenges, with AbbVie having sued Genmab over Rina-S, accusing the biotech of being "willfully blind" to the alleged theft of trade secrets.

Despite this, Genmab remains bullish on the market potential for Rina-S. Following its $1.8 billion acquisition of ProfoundBio last year, Genmab has expanded its valuation of the opportunity for Rina-S from $1 billion to over $2 billion, citing a broader set of target indications.

With plans to initiate a phase 3 trial in endometrial cancer by the end of 2025, Genmab is positioning itself to potentially reshape the landscape of FRα-directed therapies in oncology.