Objective:To compare different doses and dosing regimens of RC28-E, a novel bispecific antibody that simultaneously binds vascular endothelial growth factor-A (VEGF-A) and fibroblast growth factor-2 (FGF-2), with conbercept in patients with diabetic macular edema (DME).
Design:Prospective, randomised, active comparator-controlled, open-label, multicentre, phase 2 clinical trial.cente
Participants:The trial enrolled patients aged 18 years or older with centre-involving DME, best-corrected visual acuity (BCVA) of 73 to 24 Early Treatment Diabetic Retinopathy Study (ETDRS) letters, and central subfield thickness (CST) of 300 µm or more.
Methods:Patients were assigned randomly to one of five treatment regimens: 1.0 mg RC28-E for three initial monthly doses and then every 8 weeks (1.0mgQ8); 1.0 mg RC28-E for five initial monthly doses and then on a pro re nata (PRN) basis (1.0mgPRN); 2.0 mg RC28-E for three initial monthly doses and then every 8 weeks (2.0mgQ8); 2.0 mg RC28-E for five initial monthly doses and then on a PRN basis (2.0mgPRN); or 0.5 mg conbercept for three initial monthly doses and then on a PRN basis. Assessments were made at baseline and every 4 weeks thereafter.
Main outcome measures:The primary endpoint was the change in BCVA compared with baseline at 24 and 52 weeks. Secondary endpoints included the change in CST from baseline at 52 weeks; the proportion of patients who gained/lost ≥15 letters, ≥10 letters and >0 letter in BCVA; and the number of injections and safety outcomes.
Results:The trial enrolled 156 patients. Mean improvements in BCVA in the RC28-E groups at week 24 were 7.1, 11.0, 7.4 and 10.5 letters for 1.0mgQ8, 1.0mgPRN, 2.0mgQ8 and 2.0mgPRN regimens, respectively, versus 9.7 letters for the conbercept group (p=0.146). By week 52, the RC28-E groups exhibited respective mean BCVA enhancements of 5.5, 9.5, 9.2 and 9.7 letters, compared with 8.4 letters of the conbercept group (p=0.469). Mean reductions in CST in the RC28-E groups at week 52 were −163.2 µm, −136.9 µm, −142.5 µm and −153.6 µm, versus −160.7 µm for the conbercept group (p=0.948). The Per Protocol Set analysis indicated that at 24 weeks, the BCVA improvement in the 2.0mgPRN group was significantly greater than that in the conbercept group (14.0 vs 9.8, p=0.019). In patients with poor baseline glycaemic control (HbA1c ≥7.5%), the 2.0mgPRN group showed greater BCVA improvement than the conbercept group (14.4 vs 4.2, p=0.039) at week 52. During the maintenance phase, the 2.0mgPRN group had fewer injections (2.8, 95% CI 1.8 to 3.7) compared with the conbercept group (4.4, 95% CI 3.5 to 5.2). RC28-E was generally well tolerated. The incidence of ocular adverse events in study eyes was comparable between RC28-E groups (22.6% in 1.0mgQ8 group, 26.7% in 1.0mgPRN group, 34.4% in 2.0mgQ8 group, 25.0% in 2.0 mg PRN group) and conbercept group (32.3%). The number of ocular serious adverse events was 1 (1.0mgQ8), 0 (1.0mgPRN), 1 (2.0mgQ8), 2 (2.0mgPRN) and 0 (conbercept).
Conclusions:Intravitreous RC28-E improved BCVA and CST in eyes with centre-involved DME. Compared with conbercept, the 2.0mgPRN regimen of RC28-E was recommended due to its superior efficacy in improving vision particularly for patients with poor glycaemic control, fewer treatment injections during the maintenance phase and comparable safety profile.