Trefoil Therapeutics is in the works to initiate a Phase IIb/III trial investigating its lead compound TTHX1114 in patients with oedema, chief business officer Schalon Newton told Clinical Trials Arena.

The US-based biotech expects to initiate the trial in late 2023 or early 2024. The exact number of patients is still in discussion, but Trefoil plans to enrol around 200 patients in approximately 15 sites based in the US, Newton said.

Amongst a number of clinical endpoints, the most important endpoint will be the percentage of patients who recover 15 lines of vision after the treatment. Newton noted that for almost all ophthalmology trials, the US Food and Drug Administration (FDA) wants proof of clinical significance in the improvement of vision.

Whether the Phase IIb/III trial will act as a registrational trial is still in question. Newton explained that the company may have to make the trial size bigger or conduct another trial to achieve the number of patients required for the safety requirement.

Shifting indications

A few weeks ago, Trefoil announced positive data from a Phase II trial in patients with Fuchs endothelial corneal dystrophy (FECD) who received TTHX1114 and Descemet stripping only (DSO) procedures. After the trial has started, Trefoil decided to enrol patients who were getting cataract surgery.

Newton said: “Somewhat pleasantly surprising to us, the patients that had cataract surgery did not do worse and, in fact, many of them did better.”

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He explained that as a start-up company, one of the challenges Trefoil faced in thinking about moving forward with the DSO indication is that’s going to be a relatively small market. Whereas cataract surgery represents a large market in the US, with millions of Americans seeking this procedure. Hence, the upcoming Phase IIb/III trial will focus on patients who have oedema because of surgery.

Trial in Sjogren’s syndrome

While the Phase IIb/III trial will focus on the endothelial indication, which is the back surface of the cornea, Trefoil is planning to conduct a trial with a topical eye drop formulation of TTHX1114 in epithelial indication, the front surface of the cornea.

Trefoil has an open investigational new drug (IND) application and plans to begin the Phase II trial in the early part of 2024.

The trial will recruit patients with Sjogren’s syndrome, a condition that affects parts of the body that produce fluids such as tears and saliva. Newton shared that it will be a crossover design study, where some patients first receive treatment and some placebo, and after a washout period, cohorts will swap.

In April, Trefoil completed a Phase I dose-escalation and safety trial evaluating topical TTHX1114. There were no safety events of significance across the four dose levels, Newton said. The trial dosed its first patient in January 2023.