GigaGen presents positive phase 1 data on non-blocking anti-CTLA-4 drug candidate GIGA-564

GIGA-564 demonstrated a favorable safety profile while exhibiting early signals of anti-tumor activity in solid tumors

Apr. 17, 2026 at 7:06pm

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An extreme close-up, translucent X-ray image showing the glowing, ghostly internal structures of a cancer cell against a dark, shadowy background, conveying the complex and delicate nature of cancer biology.Cutting-edge X-ray imaging reveals the intricate inner workings of a cancer cell, hinting at the potential of a new drug to selectively target and disrupt its growth.San Diego Today

GigaGen Inc., a biotechnology company and subsidiary of Grifols, is presenting positive Phase 1 data on its anti-CTLA-4 drug candidate, GIGA-564, at the American Association for Cancer Research (AACR) Annual Meeting. GIGA-564 is a non-blocking, anti-CTLA-4 monoclonal antibody designed to target CTLA-4 in a different manner than traditional CTLA-4 blocking antibodies. In this first in-human Phase 1 study, GIGA-564 has exhibited a positive safety and tolerability profile while demonstrating early signs of single agent anti-tumor activity in patients with metastatic or locally advanced solid tumors.

Why it matters

There is a continuing, unmet need for innovative therapies for solid tumors, and this early data demonstrates that GIGA-564 has the potential to improve outcomes for patients. GIGA-564's differentiated mechanism of action, which aims to selectively deplete tumor-infiltrating T regulatory cells while avoiding the broad immune activation and toxicities associated with traditional CTLA-4 blocking antibodies, could make it a promising new approach in the fight against cancer.

The details

In the Phase 1 study, GIGA-564 demonstrated a favorable safety profile, with only one dose-limiting toxicity observed. Dose escalation (up to 20 mg/kg every three weeks) was accomplished as planned and the maximum tolerated dose was not exceeded. Among the 22 patients treated whose tumor size could be evaluated, two patients exhibited partial responses and nine additional patients had stable disease, resulting in a disease control rate of 50%. The ongoing, open-label trial is being conducted by researchers at the National Institutes of Health (NIH)/National Cancer Institute (NCI), in close partnership with GigaGen.

  • The Phase 1 data was presented at the American Association for Cancer Research (AACR) Annual Meeting on April 20, 2026.
  • The data cut-off for the results presented was January 28, 2026.

The players

GigaGen Inc.

A biotechnology company advancing transformative antibody drugs for immune deficiencies, infectious diseases and checkpoint resistant cancers, and a subsidiary of Grifols.

James Gulley, MD, PhD

The study's principal investigator from the National Cancer Institute (NCI).

Carter Keller

Senior Vice President of GigaGen.

National Institutes of Health (NIH)

The government agency that is conducting the clinical trial of GIGA-564 through a Cooperative Research and Development Agreement (CRADA) with GigaGen.

National Cancer Institute (NCI)

The division of the NIH that is conducting the clinical trial of GIGA-564 through a CRADA with GigaGen.

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What they’re saying

“Observing a favorable safety profile alongside preliminary anti-tumor activity in both anti-PD-1 refractory and immuno-oncology-naïve patients is particularly noteworthy at this early stage. GIGA-564 has a differentiated mechanism of action, and I look forward to continuing to evaluate its potential in highly refractory cancers with high unmet clinical need.”

— James Gulley, MD, PhD, Principal Investigator, National Cancer Institute

“There is a continuing, unmet need for innovative therapies for solid tumors and this early data demonstrates that GIGA-564 has the potential to improve outcomes for patients.”

— Carter Keller, Senior Vice President, GigaGen

What’s next

The ongoing, open-label Phase 1 trial of GIGA-564 is continuing, and researchers are looking forward to further evaluating the drug's potential in highly refractory cancers with high unmet clinical need.

The takeaway

GIGA-564's differentiated mechanism of action, which aims to selectively deplete tumor-infiltrating T regulatory cells while avoiding the broad immune activation and toxicities associated with traditional CTLA-4 blocking antibodies, could make it a promising new approach in the fight against cancer. The positive early safety and efficacy signals from this Phase 1 trial suggest GIGA-564 warrants further investigation as a potential new treatment option for patients with solid tumors.