Noxxon Pharma NV, of Berlin, said it inked a collaboration agreement with Merck & Co. Inc., of Kenilworth, N.J., to conduct a phase I/II trial testing Noxxon's anti-CXCL12 agent, NOX-A12, in combination with Merck's anti-PD-1 antibody Keytruda (pembrolizumab) in patients with metastatic solid tumors that do not usually respond to checkpoint inhibitor monotherapy.