Corbus Pharmaceuticals has posted the first Western clinical data on its would-be rival to Pfizer’s Padcev. The overall readout is in line with the Chinese data that drummed up excitement in the antibody-drug conjugate (ADC) last year, but investors sent Corbus’ stock down 10% in premarket trading.
Massachusetts-based Corbus licensed the Nectin-4-directed ADC in 2023. The deal saw China’s CSPC Pharmaceutical grant Corbus rights to the drug candidate in markets including the U.S. and the EU in return for $7.5 million upfront. The next year, CSPC reported a 28% response rate in 25 people in a Chinese phase 1 trial, offering early encouragement that the ADC could be a challenger to Padcev.
Friday, Corbus shared new data at the 2025 American Society of Clinical Oncology Genitourinary Cancers Symposium that suggest the efficacy seen in the Chinese trial has translated to Western populations. The new data come from a phase 1 trial that enrolled patients in the U.S. and the U.K.
Corbus reported a 27% response rate in 26 evaluable patients in the Western trial. The study mirrored the four highest doses used in the Chinese trial but featured some differences. Corbus included a wider range of tumor types and, unlike CSPC, allowed patients to enroll regardless of their individual Nectin-4 levels. The biotech reported responses in patients with low H-scores for Nectin-4.
Like in the Chinese trial, Corbus saw responses in patients with bladder and cervical cancer. The bladder data may be what has investors antsy, with the biotech reporting one response in four patients. The 25% response rate is down from the 44% seen in nine patients in China, although the small size of the arm makes it hard to draw conclusions. One of the two cervical cancer patients had a complete response.
The Western trial suggests there may also be an opportunity for the ADC in head and neck cancer, with four of the seven patients with that tumor type responding to the therapy. While the cohort is small, the response rate is currently way above the 24% Padcev has achieved in the indication.
Corbus is investing in the asset in the belief the ADC has an advantage over Pfizer because it has a longer half-life and lower drug antibody ratio. The biotech believes those differences may translate into reduced dosing frequency and higher doses than Pacdev, an ADC that Pfizer picked up in its $43 billion acquisition of Seagen. Corbus is now working to optimize the ADC dose.
Safety is one area Corbus could differentiate its ADC, with the biotech noting fewer patients on the drug candidate had peripheral neuropathy and skin toxicity than in Pacdev studies. Eye disorders looked like a safety concern in the Chinese trial, with 79% of people on one dose having a reaction, but Corbus’ steps seem to have mitigated the risk. Eye reaction rates were lower and no patients dropped out over them.