Trillium Therapeutics Inc. announced that it has initiated dosing in its second Phase 1 clinical trial with TTI-621 (SIRPaFc) in patients with relapsed or refractory percutaneously-accessible solid tumors and mycosis fungoides. Trillium is developing TTI-621 as a novel checkpoint inhibitor of the innate immune system, and the drug is currently being evaluated in an ongoing 10-cohort Phase 1b study in patients with relapsed or refractory hematologic malignancies. This two-part clinical trial is designed as a multi-center, open-label Phase 1a/1b trial, and is evaluating TTI-621 as a single-agent in patients that have relapsed or refractory percutaneously accessible solid tumors or mycosis fungoides (NCT02890368). The escalation phase will include single or multiple doses of TTI-621 delivered by intratumoral injections, which will be followed by an expansion phase during which one or more selected dose levels of TTI-621 will be tested.