4D pharma plc announced updated clinical data from Part B of its signal finding study of MRx0518 in combination with MSD's anti-PD-1 therapy, KEYTRUDA® (pembrolizumab) in patients with solid tumors that have progressed on a prior immune checkpoint inhibitor (ICI). The primary efficacy endpoint for Part B of the study is more than three out of 30 patients per tumor group achieving clinical benefit, defined as complete response, partial response, or stable disease for at least six months. In March 2022, it was announced that 4 patients in the RCC cohort had experienced durable stable disease.

At the time 4D pharma plc was placed into administration it was agreed that patient recruitment into the study would be placed on temporary pause but patients who had already started treatment would be allowed to continue. There were 2 Part B RCC patients on treatment at the time of administration. 4D pharma announced that one of these patients is experiencing a partial response.

Part B of the study has to date enrolled 22 patients with RCC, of which 5 out of 20 evaluable patients have achieved clinical benefit. To date, Part B of the study has enrolled 51 patients of up to a total of 120 patients with RCC, non-small cell lung cancer, bladder cancer, and head and neck squamous cell carcinoma. MRx0518 continues to be safe and well tolerated and 5 patients are continuing on treatment.

The study is being conducted in heavily pre-treated metastatic patients with solid tumors who have previously experienced clinical benefit on prior ICI therapy and subsequently developed progressive disease. The study is being conducted in collaboration with MSD (Merck & Co. Inc., Kenilworth, NJ, USA).