England-based Cycle Pharmaceuticals announced the US launch of Harliku (nitisinone) tablets yesterday, marking a major milestone as the first FDA-approved treatment for alkaptonuria (AKU), a rare inherited metabolic disorder.
Until now, there was no targeted therapy available in the US for the condition.
Alkaptonuria, also known as black urine disease, is an ultra-rare genetic disease caused by a deficiency in the enzyme homogentisate 1,2-dioxygenase.
Without this enzyme, the body cannot fully break down the amino acids phenylalanine and tyrosine, leading to a buildup of homogentisic acid (HGA), which accumulates in the body and causes dark pigmentation in connective tissues (a process called ochronosis), dark urine, severe joint and back pain, early-onset osteoarthritis and increased risk of heart and kidney complications.
The condition affects approximately one in every 1 million people in the US.
Harliku works by inhibiting an enzyme upstream in the tyrosine degradation pathway — 4-hydroxyphenylpyruvate dioxygenase — which effectively reduces the production of HGA.
The FDA approved Harliku in June 2025, and Cycle Pharmaceuticals plans to make the treatment available in US pharmacies starting in July.
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The treatment’s approval was based on data from a three-year, open-label study conducted by the National Human Genome Research Institute (NHGRI) at the NIH.
Results from the study, which enrolled 40 patients with AKU, showed up to 97% reductions of HGA in the urine of those treated with nitisinone, compared to increased HGA levels in the untreated control group.
Patients who received the treatment reported significant improvements in pain, energy and physical function, as assessed by the SF-36 health survey and six-minute walk test.
The safety profile of Harliku was consistent with what has been observed in prior studies of nitisinone. The most common side effects included elevated blood tyrosine levels, keratitis (inflammation of the cornea), low platelet and white blood cell counts and potential ocular symptoms. Because of these risks, patients on Harliku should undergo regular eye exams and routine blood monitoring to check tyrosine levels and complete blood counts.
Cycle Pharma emphasized its commitment to supporting the AKU community and working closely with healthcare professionals to facilitate patient access and ongoing monitoring.
Harliku offers a much-needed, non-invasive oral therapy for people with AKU, a significant improvement over symptom-based approaches or unapproved off-label treatments.
In the press release announcing Harliku’s launch, Jamie Ray, Director – Patient Support Program at Cycle Pharmaceuticals, said, “AKU is an ultra-rare condition with slow progression and variable presentation, which makes diagnosis and accessing appropriate care difficult. With the launch of Harliku, Cycle Vita can now provide patients with AKU the individualized support they need to navigate their treatment from diagnosis onwards.”
“The launch of Harliku marks an exciting milestone for our AKU community. As the first commercially available treatment for AKU in the United States, it will empower patients to take a more proactive role in their care, paving the way for personalized treatment discussions and helping to reduce barriers to access,” stated Nick Sireau, CEO and Chair of Trustees, AKU Society, in the release.
Cycle Pharmaceuticals also recently introduced Cycle Vita PKU, an AI-powered smartphone app launched in April 2025 to help individuals with phenylketonuria (PKU) manage medication, diet, lab results and related aspects of their treatment on the go.
Cycle Pharmaceuticals has a portfolio spanning metabolic, neurological and immunological genetic disorders such as hereditary tyrosinemia type 1, PKU and hereditary angioedema. The company is focused on pairing its innovative first-in-class therapies, like Harliku and Cycle Vita PKU, with patient-centric support programs under its Cycle Vita hub.
In January 2025, Cycle Pharmaceuticals completed its acquisition of Banner Life Sciences to obtain FDA-approved multiple sclerosis drug Bafiertam (monomethyl fumarate), broadening its MS portfolio alongside Tascenso.
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