Researchers are looking for a better way to treat people living with classical homocystinuria (HCU), a rare inherited condition. It is caused by changes in the cystathionine beta-synthase (or "CBS") gene and prevents an enzyme from working correctly in the body. This enzyme helps break down homocysteine, which is produced when the body processes methionine from protein-containing foods. This helps keep homocysteine and methionine at healthy levels. When this enzyme is not working, homocysteine and methionine build up in the blood and then spread into different tissues of the body and stop these body tissues from working normally.
People living with HCU can experience problems with their vision, bones, blood vessels, thinking, learning, and memory. Available treatments for HCU include a low-methionine diet (typically achieved by limiting protein-containing foods), a methionine-free protein supplement to help meet daily protein needs, and betaine (Cystadane®). These treatments are either not sufficient or are hard to take for many patients.
Pegtibatinase was designed by researchers to act like the CBS enzyme, which is missing or not working properly in people living with HCU. Researchers are studying whether adding pegtibatinase to standard treatment can lower homocysteine levels.
Researchers want to learn how safe and effective pegtibatinase is, how it moves through and affects the body, and how it may affect the daily lives of people with HCU.
The study plans to enroll participants from the US, Australia, Belgium, France, Germany, Ireland, Italy, Poland, Portugal, Qatar, Saudi Arabia, Spain, Turkey, and the United Kingdom. Many study visits may happen at home, depending on where you live and local regulations. Some visits may include a home nurse and telemedicine appointments with the study doctor.
Must be ≥12 to ≤65 years of age, at the time of signing the informed consent
Must have a diagnosis of classical HCU based on clinical, biochemical, and/or molecular genetic testing
Plasma tHcy ≥80 µM at Screening visit, with allowance for up to 18 participants who may be enrolled with a Screening plasma tHcy ≥50 to <80 µM
Participants who can become pregnant must have a negative pregnancy test before starting the study and must use a highly effective form of birth control (less than 1% risk of pregnancy per year) during the study and for at least 4 weeks after the last dose.
Diagnosis of Marfan syndrome, methylenetetrahydrofolate reductase (MTHFR) deficiency, or disorder of cobalamin metabolism
Concurrent disease or condition (eg, history or presence of clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, gastrointestinal, endocrine, immunologic, dermatologic, neurological, oncologic, or psychiatric disease) that would interfere with study participation or safety (excluding complications of HCU).
History of major thrombotic event (eg, cerebrovascular accident, myocardial infarction, pulmonary embolism) in the previous 6 months.
Body weight ≥160 kg.
Parallel
Pegtibatinase
DrugPegtibatinase BIW
Placebo
Other interventionvolume-matched saline SC BIW
Change from baseline in plasma tHcy levels - Weeks 6 to 12
Change between baseline and average of 6 to 12 week (6, 8, 10, and 12 week) plasma tHcy levels in participants receiving pegtibatinase vs. placebo. Baseline tHcy level defined as average of Week -3, Week -1, and Day 1 pre-dose plasma tHcy
Change from baseline in plasma tHcy levels - Weeks 16 to 24
Change between baseline and average of 16 to 24 week (16, 20, and 24 week) plasma tHcy levels in participants receiving pegtibatinase vs. placebo. Baseline tHcy level defined as average of Week -3, Week -1, and Day 1 pre-dose plasma tHcy
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