GTB-5550

B7-H3 TriKE may be particularly useful for patients with bone lesions or as consolidative therapy. Commercial manufacturing of B7-H3 TriKE (GTB-5550) has begun, and a phase I trial is expected in late 2023.

As proof of concept, a clinical trial of GTB-3550 (a CD33-targeted Tri-specific Killer Engager [TriKE] in AML) induced endogenous NK cell expansion and activation in refractory AML patients. Here we developed GTB-5550 (a B7H3 TriKE) as a novel dual camelid (cam) TriKE containing WT IL-15 and comprised of two cam engagers: targeting CD16 on NK cells and B7H3 on multiple solid tumors...Conclusions B7H3 TriKE delivers an NK cell specific IL-15 signal to expand NK cells and is highly specific against a broad array of cancers. Clinical manufacturing is underway with an IND planned to open clinical trials in 2023 in a number of solid tumors and multiple myeloma.

NK cell degranulation and IFN-gamma production of GTB-3550-treated samples were higher compared to that of control samples treated with B7H3 single domain or IL-15 alone. Ongoing experiments will evaluate functionality of GTB-5550 on FA patient samples as well as in spheroid assays. Taken together, this data shows that a GTB-5550 is able to drive NK cell activity against B7H3-expressing HNSCC cells, which presents potential for a B7H3-targeted TriKE to be used to be implemented clinically to treat HNSCC or FA-HNSCC patients.