The trial is currently enrolling advanced melanoma or triple negative breast cancer patients to investigate the effects of combining Biothera’s Imprime PGG with the immune checkpoint inhibitor Keytruda (pembrolizumab).
A summary of the clinical trial design will be presented in a poster titled “A multicenter, open-label, phase II study of PGG beta-glucan and pembrolizumab in patients (pts) with advanced melanoma (MEL) following progression on treatment with checkpoint inhibitors (CPI) or triple negative breast cancer (TNBC) failing front-line chemotherapy for metastatic disease.”
Imprime PGG is a yeast-derived product that binds to recognition receptors on innate immune cells, providing a critical danger signal that triggers a coordinated immune response. Cancer cells often lack these danger signals, suggesting that Imprime may help the immune system recognize and attack the tumors.
Cancers can also directly avoid a T-cell based attack by expressing the checkpoint inhibitor PD-L1, which binds to the PD-1 receptor on immune cells, sending a “do not kill” signal.
The Phase 2 IMPRIME-1 trial (NCT02981303) is investigating the combination of PGG beta-glucan and Keytruda, an antibody targeting the PD-1 protein, which participates in cancer cell survival.
The study is designed to be conducted in two parts. Stage 1 will enroll 12 patients with advanced melanoma and 12 triple negative breast cancer patients whose tumor progressed despite previous treatments. All participants must be positive for anti-beta glucan antibodies (ABA).
If the treatment demonstrates effectiveness and a good safety profile, 17 patients with melanoma and 30 patients with triple negative breast cancer will be enrolled in the second part of the study.
The trial’s main objective is tumor response and safety, but researchers will also assess other parameters, such as time to regression, duration of response, progression-free survival, and overall survival.
The study will also investigate how the PGG beta-glucan and Keytruda behave in the body and in the tumor (pharmacokinetics). They will also try to identify an ABA biomarker, markers of immune system activation, and changes in the tumor immune microenvironment.
Biothera and Merck also have clinical research agreements to evaluate the Imprime PGG, Keytruda combo in patients with head and neck squamous cell cancer and non-small cell lung cancer. Imprime PGG has already been tested as single agent or in combination therapies in more than 400 subjects with mutiple cancer types, and has shown a favourable safety profile.
According to the American Cancer Society, about 87,110 new melanomas will be diagnosed in 2017 (about 52,170 in men and 34,940 in women).