Two prospective, randomized, parallel-group, sham procedure/vehicle-controlled trials (Study 1 [NCT03442751] and Study 2 [NCT05759559]) were conducted to evaluate the safety and efficacy of epithelium-on corneal collagen cross-linking (CXL) using riboflavin 5'-phosphate ophthalmic solutions with UV-A irradiation and supplemental oxygen in patients with keratoconus.
In both trials, eligible eyes were randomized to receive CXL treatment or sham procedure/vehicle control in a 2:1 treatment allocation at the baseline visit. Aphakic patients and pseudophakic patients without a UV-blocking intraocular lens were excluded. Both eyes of a patient could be enrolled in the trial; however, one eye was treated first, and the second eye was treated between 1 week and 3 months after the first eye. Eyes were evaluated at 1 day, 3 days, 1 week, and 1, 3, 6, and 12 months post-treatment.
In Study 1, eyes randomized to sham procedure/vehicle control were permitted to receive CXL treatment after month 6 and were followed an additional 6 months. The primary efficacy endpoint was at month 6 post-treatment and the secondary efficacy endpoint was at month 12 post-treatment. In Study 2, the primary efficacy endpoint was at month 12 post-treatment and the secondary efficacy endpoint was at month 6 post-treatment.
In Study 1, a total of 280 eyes of 201 patients were randomized into the trial, of which 279 eyes were treated: 189 eyes received CXL treatment and 90 eyes initially received sham procedure/vehicle control. A statistically significant treatment effect was demonstrated at month 6, based on the difference in change from baseline in maximum corneal curvature (Kmax) between the CXL treatment group and sham procedure/vehicle control group (Table 1).
Table 1. Study 1: Mean Baseline Kmax (D) and Change from Baseline Kmax (D)| Visit | CXL Treatment (N=189) | Sham Procedure/ Vehicle Control (N=90) | Treatment Difference (95% CI) P-value |
|---|
| Randomized eyes that received study treatment |
| Baseline Mean (standard deviation) Kmax | 59.4 (9.1) | 59.3 (9.1) | |
| Month 6 LS Mean change from baseline and corresponding 95% CIs obtained from a RMMM ANCOVA model with treatment as a factor and the baseline Kmax value and baseline keratoconus severity as covariates. Missing post-baseline Kmax data were handled by multiple imputation procedure for month 6. | -0.3 (-0.6, -0.0) | 0.6 (0.2, 1.1) | -1.0 (-1.5, -0.4) P<0.01 |
| Month 12 Missing post-baseline Kmax data were handled by last observation carried forward method for month 12 in Sham Procedure/Vehicle Control eyes that received CXL treatment after month 6. | -0.4 (-0.7, -0.2) | 0.7 (0.3, 1.1) | -1.1 (-1.6, -0.6) P<0.01 |
In a subgroup analysis of patients in this trial at month 6, younger patients (< 29 years) experienced a treatment effect of -2.0 D, as a combination of improvement in the CXL treatment arm (-0.7 D) and deterioration in the sham procedure/vehicle control arm (1.3 D). Older patients (≥ 29 years) did not experience improvement at month 6 in either arm.
In Study 2, a total of 312 eyes of 208 patients were randomized into the trial, of which 312 eyes were treated: 200 eyes received CXL treatment and 112 eyes received sham procedure/vehicle control. A statistically significant treatment effect was demonstrated at month 12, based on the difference in change from baseline in Kmax between the CXL treatment group and sham procedure/vehicle control group (Table 2).
Table 2. Study 2: Mean Baseline Kmax (D) and Change from Baseline Kmax (D)| Visit | CXL Treatment (N=200) | Sham Procedure/ Vehicle Control (N=112) | Treatment Difference (95% CI) P-Value |
|---|
| Randomized eyes that received study treatment |
| Baseline Mean (standard deviation) Kmax | 58.0 (8.0) | 58.1 (8.6) | |
| Month 6 LS Mean change from baseline and corresponding 95% CIs obtained from a RMMM ANCOVA model with treatment as a factor and the baseline Kmax value and baseline keratoconus severity and age stratum as covariates. Missing post-baseline Kmax data were handled by multiple imputation procedure. | -0.4 (-0.6, -0.2) | 0.1 (-0.1, 0.4) | -0.6 (-0.9, -0.2) P<0.01 |
| Month 12 | -0.5 (-0.7, -0.3) | 0.4 (0.1, 0.8) | -1.0 (-1.3, -0.6) P<0.01 |
In a subgroup analysis of patients in this trial at month 12, younger patients (< 30 years) experienced a treatment effect of -1.1 D, as a combination of improvement in the CXL treatment arm (-0.5 D) and deterioration in the sham procedure/vehicle control arm (0.5 D). Older patients (≥ 30 years) in the CXL treatment arm experienced comparable improvement (-0.6 D) as younger patients (-0.5 D); however, in the sham procedure/vehicle control arm, older patients (-0.0 D) did not deteriorate as much as younger patients (0.5 D).