Complement Therapeutics GmbH (CTx) has received clearance from the FDA for its Investigational New Drug (IND) application for CTx001, the company’s lead gene therapy candidate.

The approval enables the launch of the Opti-GAIN Phase 1/2 clinical trial in patients with Geographic Atrophy (GA) secondary to age-related macular degeneration (AMD).

CTx001 is an adeno-associated virus (AAV)-based gene therapy designed to deliver a truncated version of Complement Receptor 1 (mini-CR1), providing long-term modulation of the classical and alternative pathways of the complement system. GA, an advanced form of dry AMD, leads to irreversible vision loss and currently has limited therapeutic options.

The Opti-GAIN (Optimised Geographic Atrophy INterventional) trial is a first-in-human, open-label Phase 1/2 study that will assess the safety, tolerability, and preliminary efficacy of CTx001 as a potential one-time treatment for GA. The study will enrol participants across leading retinal centres, with first patient dosing expected in the US in Q1 2026.

Data from i-GAIN, a natural history study with over 230 participants in the UK and US, informed the trial design. The study provided insights into disease progression, imaging biomarkers, and patient stratification, which will guide participant selection and monitoring in Opti-GAIN.

Dr Rafiq Hasan, chief executive officer of Complement Therapeutics, said: “FDA clearance of the IND for CTx001 is a major milestone for Complement Therapeutics and our mission to transform the treatment landscape for GA. It is a testament to the dedication, talent, and vision of our team that we’ve progressed from a university spinout to a clinical-stage company in just four years. 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.”

The company emphasises that the Opti-GAIN trial represents a step towards evaluating a potential one-time intervention in a condition affecting an estimated 5 million people globally, including 1.5 million in the US. By targeting multiple pathways of the complement cascade, CTx001 aims to reduce the progressive vision loss associated with GA, offering a novel approach compared with current supportive care options.

The study will monitor participants for both safety and signs of efficacy, using imaging biomarkers and functional measures of vision. Outcomes from Opti-GAIN could inform the design of later-stage trials and contribute to a better understanding of complement modulation in AMD.