Efficacy and Safety of Branched Chain Amino Acids on Retinitis Pigmentosa: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

Purpose: The aim of this study was to investigate the efficacy and safety of orally administered branched-chain amino acids (BCAAs) on disease progression in patients with retinitis pigmentosa (RP). Methods: A double-blind, randomized, placebo-controlled study was conducted at the Kyoto University Hospital. Seventy patients with RP aged 20 years or above were randomly assigned to the TK-98 (a combination of BCAAs in granule form) or placebo group. One packet (4.15 g) of the study drug was administered orally thrice daily for 78 weeks. Results: There was no significant difference in the rate of change in the total point score, the primary endpoint, between the TK-98 (-52.4 ± 10.3 dB/year) and placebo (-42.9 ± 13.8 dB/year) groups. Ellipsoid zone length decreased by -76.5 ± 8.9 and -95.5 ± 12.2 µm/year in the TK-98 and placebo groups, respectively; although this difference was not significant, the TK-98 group showed slower degeneration. No serious adverse events were associated with the oral administration of TK-98 in patients with RP. Conclusions: This study did not yield conclusive evidence supporting BCAA combination granules' effectiveness in slowing visual field progression in patients with RP. An insignificant trend toward a slower reduction in ellipsoid zone length was found in morphological tests. Further studies are required to fully understand the potential benefits of BCAA supplementation in RP. Translational Relevance: Our study demonstrates the safety of administering BCAAs to patients with RP. Accordingly, larger, more homogeneous clinical studies with longer durations may suggest their potential as therapeutic agents.