Phase 1/2 Trial Combines GI-102 With Pasritamig to Strengthen T-Cell Immunotherapy in Advanced Prostate Cancer

A newly registered phase 1/2 clinical trial will investigate whether combining two immunotherapies with complementary mechanisms can improve treatment outcomes in men with metastatic castration-resistant prostate cancer (mCRPC). The study, known as JET-201, plans to enrol 107 patients in the United States and South Korea.

The combination brings together pasritamig (JNJ-78278343), a bispecific antibody designed to redirect T cells towards prostate cancer, and GI-102, an experimental immune-stimulating fusion protein.

Pasritamig works by simultaneously binding to KLK2, a protein associated with prostate cancer cells, and CD3, a component of the T-cell receptor complex. By bringing T cells into close contact with malignant cells, it aims to trigger an immune attack against the tumour.

GI-102 takes a different approach. It combines a CD80 component with a modified interleukin-2 (IL-2) signaling system, designed to stimulate immune-cell activity. The rationale is straightforward: pasritamig directs T cells towards cancer cells, while GI-102 may help strengthen their antitumor activity.

Importantly, pasritamig has already demonstrated preliminary clinical activity when used alone.

In a previously published phase 1 study involving 174 heavily pretreated patients with mCRPC, 14 of 33 patients (42.4%) in the recommended-dose efficacy population achieved a PSA reduction of at least 50%. Median radiographic progression-free survival in this group was 7.85 months.

The new JET-201 study will begin with a safety evaluation to establish an appropriate combination dose, followed by an expansion stage designed to investigate antitumour activity, including PSA responses.

Clinical trial.