A promising new immunotherapy called CD-001 has been green lighted to start a phase 1 clinical trial in solid tumors. While immune checkpoint inhibitors have revolutionized cancer treatment over the past decade, their success in prostate cancer has been limited. CD-001 offers a novel approach that could change this landscape by combining two powerful immune-boosting strategies into a single drug.

CD-001 is a fusion protein that simultaneously blocks the PD-1 immune checkpoint—a mechanism tumors use to evade immune attack—while delivering a mutated form of the cytokine IL-21 directly to PD-1 positive T cells. This dual action aims to awaken the body’s own immune system more effectively than current therapies. IL-21 is known to enhance the activity and proliferation of CD8+ T cells, the immune cells responsible for killing cancer cells. By focusing IL-21 delivery specifically on T cells already engaged with the tumor, CD-001 hopes to maximize tumor-killing effects while minimizing the systemic side effects that have limited the use of cytokine therapies in the past.

Preclinical studies have demonstrated that CD-001 binds strongly to both PD-1 and the IL-21 receptor and shows superior antitumor activity compared to anti-PD-1 treatment alone or combined with free IL-21. These studies in mouse models of melanoma, lung cancer, and lymphoma revealed enhanced expansion of tumor-reactive CD8+ T cells, a critical factor in overcoming the immunosuppressive environment (typical of prostate tumors). Toxicology tests in primates also showed a favorable safety profile, with no significant cardiovascular or neurological issues and manageable immune-related side effects that resolved after treatment ended.

Although prostate cancer was not specifically tested in these early studies, the mechanism of CD-001 is highly relevant to this disease. Prostate tumors often create a hostile environment that suppresses immune responses, and single-agent checkpoint inhibitors have shown only modest benefits. The ability of CD-001 to both block inhibitory signals and simultaneously stimulate T cells could overcome this resistance and lead to more durable responses. This is particularly important for metastatic castration-resistant prostate cancer patients, who currently have limited effective treatment options beyond hormone therapies and chemotherapy.

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