CANBERRA: A Phase II Randomized Clinical Trial to Test the Therapeutic Potential of Oral Vicasinabin in Diabetic Retinopathy

Abstract

Objective

Nonproliferative diabetic retinopathy (NPDR) is a progressive disease that can lead to blindness. Current therapies for NPDR are invasive and not extensively used or accessible until the disease progresses, pointing to the need for an early noninvasive treatment. The objective of CANBERRA was to assess the safety, tolerability, and efficacy of oral administration of vicasinabin (RG7774) on the severity of diabetic retinopathy (DR) in participants with moderately severe to severe NPDR and good vision.

Design

CANBERRA was a global, multicentric randomized, double-masked, parallel-group, placebo-controlled, phase II study. The study duration was 36 months.

Participants

A total of 139 treatment-naïve patients with type 1 or type 2 diabetes mellitus and Diabetic Retinopathy Severity Scale (DRSS) levels of 47 or 53 in ≥1 eye were enrolled.

Intervention

Eligible patients were randomized 1:1:1 to 36 weeks of daily oral placebo, vicasinabin 30 mg, or vicasinabin 200 mg. Participants were followed for an additional 12 weeks.

Main Outcome Measures

The primary safety objective was to evaluate the safety and tolerability of vicasinabin by the frequency and severity of adverse events (AEs). The primary efficacy objective was to assess the effect of vicasinabin on the severity of DR, assessing the proportion of participants with ≥2-step improvement in DRSS from baseline at week 36 in the study eye.

Results

Results are presented in the following order: placebo, vicasinabin 30 mg, vicasinabin 200 mg; 47, 48, and 44 participants were enrolled. Baseline characteristics were balanced. Adherence to treatment was approximately 90%, and pharmacokinetic analysis showed dose-dependent plasma exposure to vicasinabin. The primary efficacy endpoint was not met: the percentage of participants who improved their DRSS by ≥2 steps at week 36 from baseline were 7.9, 9.5, and 5.7, without statistically significant differences. The systemic and ocular safety profiles of vicasinabin were favorable, and AEs distributed evenly across arms. Vicasinabin did not induce changes in glycemic control or any kidney function or cardiovascular parameters. Three patients in the placebo arm discontinued the study due to serious AEs not related to the drug.

Conclusions

At the doses tested, vicasinabin did not improve DRSS in participants with NPDR. The role of the cannabinoid system in DR remains elusive.

Trial Registration

ClinicalTrials.gov identifier: NCT04265261. EUDRACT number: 2019-002067-10.

Financial Disclosure(s)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.