CHICAGO — Immunocore reported Friday that in an early-stage study, 56% of melanoma patients who received its experimental drug achieved disease control — a measurement that’s not typically touted by drug companies, but that Immunocore says is most predictive of how well its treatment can stave off cancer progression.
In the Phase 1 study, 47 melanoma patients who had exhausted other treatment options received brenetafusp. Of those, 36 were included in the efficacy analysis. Four patients achieved a partial response, meaning their tumors shrank by at least 30%, and 16 achieved stable disease — the combination of the two measures makes up disease control. The data were presented Friday afternoon at the American Society of Clinical Oncology annual meeting.
When an earlier cut of data was shared last week, Immunocore’s shares slid around 10%. “We suspect market disappointment relates to a 13% objective response rate reported for brenetafusp — far short of the current standard of care,” Mizuho analyst Graig Suvannavejh wrote in a note last week. But Suvannavejh also said the focus should instead be on the disease control rate and that his team was “pleased with what we saw.”
David BermanThe way Immunocore’s drug works explains why the response rate may underestimate the benefit and why the company instead relies on disease control, Immunocore’s head of R&D David Berman told Endpoints News.
“We’re seeing much more robust T cell infiltration into the tumor than is seen with anti-CTLA-4 and anti-PD-1,” Berman said, referring to checkpoint inhibitors. “As a consequence of that very robust T cell infiltration, what we found is that measuring benefit is different than checkpoints.”
Immunocore’s drug brenetafusp, which entered Phase 3 in December, is part of a rapidly expanding class of treatments known as bispecific T cell engagers. The treatments attach to T cells with one arm and a cancer marker with the other, bringing T cells to tumor cells to kill them. While other T cell engagers latch onto a marker outside the tumor cell, Immunocore designs its drugs to target proteins from both inside and outside tumor cells.
Brenetafusp targets PRAME, a protein found in melanomas with a very literal full name: preferentially expressed antigen in melanoma.
Five patients in the study were PRAME-negative, acting like an “internal control” for the small early-stage trial, according to Berman. Those patients went a median of just over two months without cancer progression, compared to patients who were PRAME-positive who went a median of just over four months. At half a year, 95% of the patients who were PRAME-positive were still alive compared to two of the five PRAME-negative patients.
Nine melanoma patients also received brenetafusp in combination with Merck’s checkpoint inhibitor Keytruda. All of them had received at least one checkpoint inhibitor previously, and many had received two. Of seven patients evaluated for efficacy, four achieved disease control, according to Immunocore.
The most common treatment-related adverse events were mild cases of cytokine release syndrome and rash, occurring mostly during the first three doses, according to Immunocore.
The company has a Phase 3 trial underway combining brenetafusp with Bristol Myers Squibb’s Opdivo as a first treatment option for metastatic skin cancer. Immunocore also announced Wednesday it was converting a Phase 2/3 study of its approved T cell engager Kimmtrak as a second treatment option in skin cancer into a Phase 3 study. Kimmtrak is currently approved in uveal melanoma, a type of eye cancer, and generated $238.7 million in sales in 2023.