GigaGen presents positive phase 1 data on non-blocking anti-CTLA-4 drug candidate GIGA-564 at AACR 2026

Barcelona, Spain, April 17, 2026 – GigaGen Inc., a biotechnology company advancing transformative antibody drugs for immune deficiencies, infectious diseases and checkpoint resistant cancers, and a 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. To date 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.

“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,” said James Gulley, MD, PhD, the study’s principal investigator from NIH’s NCI. “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.”

Carter Keller, Senior Vice President of GigaGen, added, “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.”

Poster Presentation Details:

Title: Preliminary data from the first-in-human Phase 1 study of GIGA-564, a non-blocking anti-CTLA-4 antibody designed to deplete intratumoral Tregs in advanced or metastatic solid tumors.

Session: PO.CT01.01

Poster number: CT114/6

Presentation Date: April 20, 2026 at 2:00 PM PST

Presenter: James Gulley, MD, PhD, National Cancer Institute

Location: San Diego, CA (USA)

Summary of Results as of Data Cut-Off of January 28th, 2026 (N = 26 patients received one or more doses of GIGA-564):

• 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 as per RECIST 1.1 criteria
  • Nine additional patients had stable disease per RECIST 1.1, including two patients who met the protocol-defined criteria for minor response (>= 20% reduction in target lesions).
  • The disease control rate (PR +SD) was 50%.

The ongoing, open-label trial is being conducted by researchers at NIH/NCI, in close partnership with GigaGen. For more information about the trial, refer to clinicaltrials.gov identifier: NCT06258304.

For patients interested in enrolling in this clinical trial, please call NCI’s toll-free number: 1-800-4-Cancer (1-800-422-6237) (TTY: 1- 800-332-8615); visit the website: https://trials.cancer.gov; and/or email: NCIMO_referrals@mail.nih.gov.

About GIGA-564

GIGA-564, a fully human monoclonal antibody, distinguishes itself from currently available anti-CTLA-4 drugs. Previous anti-CTLA-4 drugs were designed to strongly block CTLA-4's interaction with its ligands, thereby enhancing broad activation of T effector cells. This approach has been associated with heightened systemic immune-related side effects. Moreover, recent insights reveal that previous anti-CTLA-4 drugs contribute to an increased broad proliferation of T regulatory cells (Tregs), which may dampen their intended effect of activating cytotoxic T cells that are vital for attacking tumors. In comparison, GIGA-564's uniqueness stems from its ability to target CTLA-4 without blocking CTLA-4 binding to its ligands, allowing it to selectively deplete Tregs in the tumor microenvironment and enhance local cancer-killing activity within the tumor. This mechanism demonstrated increased anti-tumor efficacy while limiting drug toxicities pre-clinically.