FDA Gives Orphan Drug Status to Potential Multiple Myeloma Immunotherapy

The U.S. Food and Drug Administration (FDA) has granted orphan drug designation to Harpoon Therapeutics‘ investigational immunotherapy HPN217 as a possible treatment of multiple myeloma.

The designation encourages the development of potential therapies for rare and serious diseases by granting them various financial and regulatory benefits. These include exemptions from certain fees, trial protocol assistance, and seven years of market exclusivity upon approval.

“Orphan Drug Designation for multiple myeloma represents a significant milestone in the development of HPN217 and recognizes its potential to address a significant unmet medical need for the patients suffering from this condition,” Jerry McMahon, PhD, president and chief executive of Harpoon Therapeutics, said in a press release.

HPN217 is a form of immunotherapy that redirects immune T-cells, the most potent cells in the fight against cancer, to attack tumor cells. The treatment is a T-cell engager, developed using Harpoon’s Tri-specific T-cell Activating Construct (TriTAC) platform, that acts as a bridge between immune cells and cancer cells by binding to proteins on the surface of both cell types.

Specifically, HPN217 binds to the CD3 surface receptor on immune T-cells, and to the B-cell maturation antigen (BCMA) on myeloma cells, linking them and activating an immune response.

While the mechanism is similar to that of a bispecific antibody, HPN217 is much smaller and more stable in the bloodstream, potentially allowing a more convenient dosing (once a week) and providing greater benefits.

After finding anti-cancer activity in preclinical studies, Harpoon launched a Phase 1/2 trial (NCT04184050) to investigate the safety and preliminary signs of effectiveness of HPN217 in people with relapsed or refractory multiple myeloma.

The trial started dosing in April, aiming to enroll 70 patients who had received at least three prior lines of treatment, including a proteasome inhibitor, an immunomodulatory agent, and a CD38 inhibitor, and had no additional available therapies.

The U.S.-based trial is two-fold. In a first, dose-escalation part, patients will receive ascending doses of HPN217, delivered weekly via into-the-vein infusions, to establish the maximum tolerated dose and identify the optimal dose for additional testing.

The second part is a dose expansion phase designed to continue evaluating the optimal dose in an additional group of patients with no previous BCMA-targeting treatments.

According to Harpoon, interim data from the first part has shown that the therapy is well tolerated, without dose-limiting toxicities. Additional data is expected to be presented in upcoming months, and dosing for the expansion phase is anticipated for this year’s second half.

“I am pleased with the clinical progress we are making with this program and we are planning to present interim data from the ongoing Phase 1/2 dose escalation trial later this year,” McMahon said.

HPN217 is being developed under a global license and option agreement with AbbVie.