Ovarian Cancer Patients Being Recruited to Test HPN536 Immunotherapy in Phase 1/2a Trial

Harpoon Therapeutics has begun dosing participants in its Phase 1/2a trial evaluating the investigational immunotherapy HPN536 in patients with advanced cancers that produce the mesothelin protein.

The study (NCT03872206) will first enroll 20 ovarian cancer patients to determine the treatment’s safety and the best therapeutic dose. Then, 60 additional patients — 20 with ovarian cancer, 20 with pancreatic cancer, and 20 with mesothelioma — will be included in the second part to continue assessing HPN536’s safety and efficacy.

“We are pleased with the rapid progress of our clinical programs, based on our proprietary TriTAC [tri-specific T-cell activating construct] platform, with patient dosing now underway for our second product candidate, HPN536, that targets mesothelin,” Natalie Sacks, MD, chief medical officer of Harpoon Therapeutics, said in a press release.

“The dose escalation portion of the trial will focus on patients with ovarian cancer, where mesothelin is over expressed in a high percentage of patients,” she said.

While antibodies that bind and bridge cancer cells and immune cells have shown promising therapeutic potential in clinical trials, Harpoon created HPN536 to bind not two, but three distinct targets.

Among the three targets, two are still meant to bind cancer and immune cells and bring them together for a more efficient cancer targeting. The third one, however, binds albumin — the most common protein in blood — and is meant to increase the stability of the overall product, allowing for more convenient dosing regimens.

Importantly, these products are one-third the size of an antibody, and are expected to enter solid tumors much more efficiently than single or bi-specific antibodies.

HPN536 has been shown to activate T-cells against the mesothelin protein in monkeys without any safety concerns. It also prevented tumor growth in mice.

“Harpoon’s unique approach to T cell engagement may offer appealing advantages over other T cell therapies and, in addition, provide meaningful efficacy with improved patient management based on the convenience of once weekly intravenous dosing,” said Gerald McMahon, PhD, president and CEO of Harpoon.

“We look forward to exploring this target, where CAR (chimeric antigen receptor) expressing T cells targeting mesothelin have shown early evidence of clinical benefit,” he added.

The ongoing clinical trial is recruiting participants at the Sarah Cannon Research Institute at Tennessee Oncology in Nashville. For additional information, go here.