Regeneron Achieves 73% Response Rate with Ubamatamab in Phase 1/2 LGSOC Trial

A 73% objective response rate in a heavily pre-treated population signals that Regeneron's MUC16xCD3 bispecific antibody, ubamatamab, is moving toward a confirmatory Phase 3 trial with meaningful clinical data behind it, and that the manufacturing and QA infrastructure required to support scale-up of this biologic will need to be in place well ahead of any potential approval.

Data from an ongoing Phase 1/2 trial in recurrent platinum-resistant ovarian cancer were presented in a late-breaking plenary session at the IGCS 2026 Annual Global Meeting. The LGSOC subset included 19 patients who had received a median of four prior lines of therapy. Among the 11 patients treated at the 800 mg monotherapy dose, the trial recorded a 73% ORR (95% CI: 39.0–94.0), a nine-month median duration of response, and an 11-month median progression-free survival. All responses were partial responses.

For context, historical ORRs in recurrent advanced LGSOC with chemotherapy and endocrine therapy have remained below 15%. The only currently approved therapy carries a 44% ORR, but only in biomarker-selected patients representing roughly 30% of the LGSOC population. Ubamatamab achieved its results without requiring biomarker selection, a distinction that broadens the eligible patient population and complicates neither enrollment nor companion diagnostic requirements.

Ubamatamab is a bispecific antibody engineered to bridge MUC16-expressing tumor cells with CD3-positive T cells, driving local T-cell activation at the tumor site. Bispecific antibody manufacturing carries inherent complexity: dual-specificity constructs require tightly controlled upstream bioprocessing, rigorous charge-variant characterization, and comparability protocols that will face scrutiny under 21 CFR Part 211 and ICH Q10 quality system expectations as the program transitions from Phase 1/2 to Phase 3 scale.

Regeneron has already begun enrolling a single-arm, potentially registrational LGSOC cohort at the 800 mg dose and has indicated it will discuss the data with the FDA in the coming months. A randomized, controlled confirmatory Phase 3 trial is also planned. For contract manufacturers and QA directors engaged with oncology biologics, the near-term FDA discussions will be a key indicator of the agency's expectations around process validation and lot-release specifications for this class of molecule.

The confirmatory Phase 3 trial design and the outcome of Regeneron's FDA discussions will set the process validation benchmarks that manufacturers supporting this program will need to meet before any submission package is filed.

Source: Regeneron Pharmaceuticals via GlobeNewswire, 1 October 2026.