One-year pilot study on the effects of nitisinone on melanin in patients with OCA-1B
David R. Adams, Supriya Menezes, Ramon Jauregui, Zaheer M. Valivullah, Bradley Power, Maria Abraham, Brett G. Jeffrey, Angel Garced, Ramakrishna P. Alur, Denise Cunningham, Edythe Wiggs, Melissa A. Merideth, Pei-Wen Chiang, Shanna Bernstein, Shosuke Ito, Kazumasa Wakamatsu, Rhona M. Jack, Wendy J. Introne, William A. Gahl, Brian P. Brooks
David R. Adams, Supriya Menezes, Ramon Jauregui, Zaheer M. Valivullah, Bradley Power, Maria Abraham, Brett G. Jeffrey, Angel Garced, Ramakrishna P. Alur, Denise Cunningham, Edythe Wiggs, Melissa A. Merideth, Pei-Wen Chiang, Shanna Bernstein, Shosuke Ito, Kazumasa Wakamatsu, Rhona M. Jack, Wendy J. Introne, William A. Gahl, Brian P. Brooks
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Clinical Research and Public Health Genetics Ophthalmology

One-year pilot study on the effects of nitisinone on melanin in patients with OCA-1B

Abstract

BACKGROUND. Oculocutaneous albinism (OCA) results in reduced melanin synthesis, skin hypopigmentation, increased risk of UV-induced malignancy, and developmental eye abnormalities affecting vision. No treatments exist. We have shown that oral nitisinone increases ocular and fur pigmentation in a mouse model of one form of albinism, OCA-1B, due to hypomorphic mutations in the Tyrosinase gene. METHODS. In this open-label pilot study, 5 adult patients with OCA-1B established baseline measurements of iris, skin, and hair pigmentation and were treated over 12 months with 2 mg/d oral nitisinone. Changes in pigmentation and visual function were evaluated at 3-month intervals. RESULTS. The mean change in iris transillumination, a marker of melanin, from baseline was 1.0 ± 1.54 points, representing no change. The method of iris transillumination grading showed a high intergrader reliability (intraclass correlation coefficient ≥ 0.88 at each visit). The number of letters read (visual acuity) improved significantly at month 12 for both eyes (right eye, OD, mean 4.2 [95% CI, 0.3, 8.1], P = 0.04) and left eye (OS, 5 [1.0, 9.1], P = 0.003). Skin pigmentation on the inner bicep increased (M index increase = 1.72 [0.03, 3.41], P = 0.047). Finally, hair pigmentation increased by both reflectometry (M index [17.3 {4.4, 30.2}, P = 0.01]) and biochemically. CONCLUSION. Nitisinone did not result in an increase in iris melanin content but may increase hair and skin pigmentation in patients with OCA-1B. The iris transillumination grading scale used in this study proved robust, with potential for use in future clinical trials. TRIAL REGISTRATION. ClinicalTrials.gov NCT01838655. FUNDING. Intramural program of the National Eye Institute.

Authors

David R. Adams, Supriya Menezes, Ramon Jauregui, Zaheer M. Valivullah, Bradley Power, Maria Abraham, Brett G. Jeffrey, Angel Garced, Ramakrishna P. Alur, Denise Cunningham, Edythe Wiggs, Melissa A. Merideth, Pei-Wen Chiang, Shanna Bernstein, Shosuke Ito, Kazumasa Wakamatsu, Rhona M. Jack, Wendy J. Introne, William A. Gahl, Brian P. Brooks

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Figure 6

Plasma nitisinone concentration over time by participant and overall.

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Plasma nitisinone concentration over time by participant and overall. Th...
The colored lines correspond to individual participant measurements, and the black line corresponds to mean (n = 5) across all participants. Plasma concentrations of nitisinone peaked between months 6 and 12 for participants and dropped to almost nil at month 15, which is 3 months after investigational product (IP) discontinuation. One participant chose the option to restart IP at month 18, before discontinuing it approximately 1.5 months later and completing their safety follow-up visit, resulting in the spike in mean plasma nitisinone concentration at the safety follow-up visit.