On December 29, 2016 Prima BioMed Ltd (ASX: PRR; NASDAQ: PBMD) ("Prima" or the "Company") reported interim data for its TACTI-mel (Two ACTive Immunotherapeutics in melanoma) clinical trial program for IMP321 in unresectable or metastatic melanoma patient (Press release, Prima Biomed, DEC 29, 2016, View Source [SID1234517233])s. The Database Safety Monitoring Board (DSMB) confirmed that IMP321 is safe and well tolerated at the first dose level when used in combination with a PD-1 blocking antibody and dose escalation can continue as planned.

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In this first-in-man combination Phase I study, IMP321 is combined with the PD-1 checkpoint inhibitor pembrolizumab (KEYTRUDA). Patients with unresectable or metastatic melanoma that had suboptimal or no responses to KEYTRUDA have been receiving IMP321 plus KEYTRUDA to help boost their immune responses and increase the tumour response rate to KEYTRUDA.

Initial data show no safety concerns from the combination with IMP321 at 1 mg dosage. No drug related serious adverse events have been reported and the DSMB approved the continuance of the dose escalation as planned. The trial will now proceed to the next dose level of 6 mg.

Prima’s Chief Medical Officer, Dr Frédéric Triebel, said: "The majority of metastatic melanoma patients do not respond well to KEYTRUDA, a key reason being that their tumours are poorly infiltrated by activated T cells expressing PD-1. By introducing IMP321, a first-in-class Antigen Presenting Cell (APC) activator, these patients may now be able to repopulate their tumour with more activated T cells which are responsive to KEYTRUDA. So, by combining the effect of ‘pushing the gas’ with IMP321 and ‘releasing the brake’ with KEYTRUDA we propose a rational therapeutic approach to increase the response rate by further boosting anti-tumour CD8 T cells."

Further data updates in terms of safety and activity could be expected throughout 2017.

About IMP321
IMP321, a first-in-class Antigen Presenting Cell (APC) activator based on the immune checkpoint LAG-3, represents one of the first proposed active immunotherapy drugs in which the patient’s own immune system is harnessed to respond to tumour antigenic debris created by chemotherapy. As an APC activator IMP321 boosts the network of dendritic cells in the body that can respond to tumour antigens for a better anti-tumour CD8 T cell response.