Brief Summary: |
This 3-year study will examine the safety and effectiveness of long-term use of nitisinone (Orfadin) for treating joint problems in patients with alkaptonuria, an inherited disease in which a compound called homogentisic acid accumulates. The excess homogentisic acid causes arthritis and limited joint movement. It can also cause heart valve damage and kidney stones. Patients between 30 and 80 years of age with alkaptonuria may be eligible for this study. Patients must have hip involvement, but at least one remaining hip joint. Candidates are recruited from among patients enrolled in protocol 00-HG-0141, "Clinical, Biochemical, and Molecular Investigations into Alkaptonuria." Participants may enter both protocols simultaneously. Participants are randomly assigned to one of two treatment groups: one group takes their regular medicines plus a 2-mg nitisinone capsule daily; the other group takes only their regular medicines. Patients taking nitisinone have blood tests to measure liver function 2 weeks and 6 weeks after starting treatment. Before starting therapy, all patients are admitted to the NIH Clinical Center for 4-5 days to undergo the following procedures:
- Medical history and physical examination
- 24-hour urine collection to test for sugar, protein, and other molecules
- Blood tests for liver and thyroid function, blood counts, and blood chemistries
- Blood and urine tests to measure tyrosine and other amino acids and homogentisic acid
- Bone x-rays
- Spiral CT (computed tomography) of the abdomen to detect kidney stones
- Eye examination and evaluations by specialists in rehabilitation medicine and pain, plus other consults in skin, brain, lung, heart, and kidney, as needed
All patients, whether or not they receive nitisinone, return to the Clinical Center for a 2-3 day follow-up admission every 4 months for a history and physical examination, blood tests, and two 24-hour urine collections. Every 12 months (12, 24 and 36 months after starting the study), patients also have repeat bone x-rays, spiral CT, kidney ultrasound, echocardiogram, and electrocardiogram. An MRI of the brain is done at the end of the study. Sixteen months after the end of the study enrollment period, the treated and non-treated groups are evaluated. If nitisinone has delayed the progression of joint disease in the treated group, the study continues and all patients receive the drug for the remainder of the study. If not, the study continues for another 20 months, at which time the study ends and the evaluation process is repeated. Patients who develop symptoms such as corneal crystals, pain, or severe liver or nervous system toxicity may be taken off the study. |
Detailed Description: |
Alkaptonuria is a rare metabolic disease in which homogentisic acid (HGA), an intermediary metabolite in tyrosine catabolism, accumulates due to deficiency of the enzyme homogentisic acid oxidase. Patients with alkaptonuria exhibit homogentisic aciduria and ochronosis, or dark pigmentation of various tissues due to binding of HGA and its oxidized metabolites. The ochronosis results in debilitating destruction of cartilage, arthritis, lumbosacral ankylosis, limitation of motion, and bone deterioration in later life. No effective therapy exists for alkaptonuria. However, a compound named 2-(2-nitro-4-trifluoromethylbenzoyl) - 1, 3-cyclohexanedione (nitisinone, NTBC, Orfadin) inhibits 4-hydroxyphenylpyruvate dioxygenase, the enzyme that produces HGA. Nitisinone, at doses of approximately 1 mg/kg/day, has proven safe and effective in tyrosinemia type I, which causes fatal liver disease in infants and children. Under protocol 97-HG-0201, we investigated the safety of administering a dose of nitisinone necessary to lower HGA excretion to 0.5 grams/day. We treated 9 alkaptonturia patients with nitisinone; for the 7 who received 1.05 mg twice daily, the HA fell from 4.0 plus or minus 1.8 g/24h to 0.2 plus or minus 0.2 g/24h (normal 0.028 + 0.015 g/24h, n=10). This reduction in HGA production can be expected to retard the progression of joint disease in alkaptonuria. Plasma tyrosine levels rose from 67 + 18 microliter M to 760 plus or minus 181 microliter M, but no patient experienced ophthalmologic complications during the 3-4 month study. Therefore, we intend to perform a randomized, controlled clinical trial of nitisinone (2 mg daily) to determine if this treatment proves beneficial for the joint symptoms of alkaptonuria. Patients will be examined at the NIH Clinical Research Center every 4 months for 3 years. Hip joint range of motion will serve as the primary outcome parameter, and nitisinone (Orfadin) will be provided by Swedish Orphan International through an IND obtained by William A. Gahl. |