ASCO24: Immunocore Falls After Disappointing Melanoma Bispecific Data

Immunocore's stock experienced a significant drop of up to 14% on Friday following the release of initial Phase I trial data for its PRAME-targeting bispecific IMC-F106C, also known as brentafusp, in patients with metastatic cutaneous melanoma. This data was eagerly anticipated in the medical community.

The initial reaction from the market was one of disappointment, primarily due to the 13% objective response rate (ORR) reported for brentafusp, which fell short of the current standard of care. However, analysts from Mizuho Securities pointed out that the focus should be on the disease control rate, which was over 60%, as it is a better predictor of survival outcomes. The analysts expressed satisfaction with the results.

The findings were revealed in an abstract ahead of the American Society of Clinical Oncology (ASCO) conference scheduled for later this month. The study involved 46 participants who had previously experienced disease progression despite receiving checkpoint inhibitor therapy. All the patients had undergone anti-PD-1 treatment, and 88% had received CTLA-4 therapy. Among the 31 patients who were evaluable, 35% showed tumor shrinkage, including four partial responses, resulting in a 13% ORR. The clinical benefit rate stood at 61%, and this rate climbed to 65% in the 26 patients whose tumors tested positive for PRAME. There was no tumor reduction observed in the five PRAME-negative subjects.

Patients with tumors expressing the PRAME biomarker demonstrated better outcomes. The median progression-free survival for these patients was 4.5 months, in contrast to just 2.1 months for PRAME-negative patients. Furthermore, 94% of PRAME-positive patients were alive at the six-month mark, compared to only 40% of those who were PRAME-negative.

Currently, Immunocore is conducting a Phase III trial, known as PRISM-MEL301, which started earlier this year. This study is evaluating the combination of IMC-F106C with Bristol Myers Squibb's immunotherapy Opdivo (nivolumab) for first-line treatment of metastatic cutaneous melanoma patients. This combination aims to provide a more effective treatment option for those newly diagnosed with this aggressive form of skin cancer.

In summary, while the initial ORR for brentafusp may not have met market expectations, the higher disease control rate and the significant benefits observed in PRAME-positive patients suggest a potentially valuable treatment option for metastatic cutaneous melanoma. The ongoing Phase III PRISM-MEL301 study will further assess the efficacy of combining IMC-F106C with Opdivo, potentially offering new hope for patients with this challenging condition.