FDA clears IND for Complement Therapeutics’ CTx001 gene therapy in geographic atrophy

The US Food and Drug Administration (FDA) has approved the Investigational New Drug (IND) application from Complement Therapeutics for CTx001, its lead gene therapy candidate.

Thanks to the IND clearance, Complement Therapeutics can now initiate the Opti-GAIN (Optimized Geographic Atrophy INterventional) phase 1/2 clinical trial in patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD).

Opti-GAIN will be an international first-in-human, open-label, phase 1/2 study designed to evaluate the safety, tolerability, and preliminary efficacy of CTx001. First dosing is expected to begin in the US during Q1 of 2026.

The company defines CTx001 as an adeno-associated virus (AAV)-based gene therapy designed to deliver a truncated version of Complement Receptor 1 (mini-CR1). According to the company, this enables long-term modulation of the “classical and alternative pathways of the complement cascade.” The company describes the complement cascade as “part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane.”¹

Furthermore, the company notes that dysregulation of the complement system is implicated in the development of several diseases, including AMD, kidney disease, and various hematological conditions. The company also noted that research conducted by the founders of the company identified the pivotal role of factor H-related proteins in the development of AMD, providing the foundation for the therapeutic strategy being pursued by the company with CTx001.¹

Rafiq Hasan, MD, CEO of Complement Therapeutics, commented on the FDA clearance in a press release from the company,¹ saying, “FDA clearance of the IND for CTx001 is a major milestone for Complement Therapeutics and our mission to transform the treatment landscape for GA. […] With Opti-GAIN, we are entering the clinic with a highly innovative gene therapy candidate that has the potential to deliver durable, one-time treatment benefits for patients affected by this devastating disease.”

According to the company, the trial design is informed by data from i-GAIN, which was a natural history study involving over 230 participants. The company states that i-GAIN “provided valuable insights into disease progression, imaging biomarkers, and patient stratification in GA.”¹

References:

1. Complement Therapeutics receives FDA IND clearance to advance CTx001 into Opti-GAIN, a phase I/II clinical trial in geographic atrophy secondary to AMD. Published October 8, 2025. Accessed October 8, 2025. https://complementtx.com/complement-therapeutics-receives-fda-ind-clearance-to-advance-ctx001-into-opti-gain-a-phase-i-ii-clinical-trial-in-geographic-atrophy-secondary-to-amd/