Prima BioMed Ltd. announced the first patient has been dosed as part of the enlarged randomised phase of its AIPAC Phase IIb clinical trial for IMP321 in metastatic breast cancer. The randomised phase of AIPAC (Active Immunotherapy PAClitaxel) will see half of the 226 patients receiving paclitaxel plus a placebo and half receiving paclitaxel in conjunction with IMP321. This follows the Dose Escalation Committee approval of the 30 mg dosage level for IMP321 and commencement of the randomised study on December 30, 2016. IMP321, a first-in-class Antigen Presenting Cell (APC) activator based on the immune checkpoint target 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.