Subjects on a standard regimen of tiopronin (cystine binding thiol drug; CBTD) plus prescribed first-line therapy (i.e. on a hydration, alkali therapy and dietary restriction) who are failing therapy will be selected for this trial.~Subjects will be encouraged to continue their usual self-selected ad-lib diets, fluid and alkali regimen and keep this regimen consistent throughout the duration of the study. Study diaries will be kept to assess consistency and drug compliance.~After completing informed consent, the enrolled subject will have an initial Screening interview. During the interview the patient will be assessed for symptoms of renal colic as well as asked about any scheduled urological procedures (a positive indication is an exclusionary criteria). At the Screening visit, a medication history will be taken and a complete physical examination, including vital signs will be done. Samples of blood and urine will be taken for clinical laboratory and urinalysis. Patients will then undergo a 12-lead ECG test.~A history of side effects with current CBTD as well as laboratory recordings of abnormalities attributable to treatment will also be recorded.~Enrolled subjects will be dosed in a sequential manner, starting with the low dose group (300 mg/day). Safety and tolerability will be monitored closely by an Independent Medical Monitor (IMM) and based on the IMM's assessment that it is safe to proceed to the higher dose (600 mg/day), subsequent subjects will be enrolled into that group. Up to 15 subjects each will be enrolled into either Group A or Group B.~Subjects will stop taking their current CBTDs for 7 days and perform a 24-hour urine collection on Day-7 and report for Day 1 Visit .~Subjects enrolled into Group A will start taking bucillamine tablets orally, three times a day preferably 1hr before or 2hrs after meals in the following sequence; 100 mg (1 tab) in the morning; 100 mg (1 tab) at noon and 100 mg (1 tab) at night. This drug regimen will continue for 7 days. Safety Visits are scheduled on Day 3 and Day 8 (End of Study Visit). Furthermore, on Day 7 a 24-hour urine collection will be performed. Instructions for handling this sample will be provided in a separate manual.~Subjects enrolled into Group B, will start taking bucillamine tablets orally, three times a day preferably 1hr before or 2hrs after meals in the following sequence; 200 mg (2 tabs) in the morning; 200 mg (2 tabs) at noon and 200 mg (2 tabs) at night. This drug regimen will continue for 7 days. Safety Visits are scheduled on Day 3 and Day 8 (End of Study Visit). Furthermore, on Day 7 a 24-hour urine collection will be performed. Instructions for handling this sample will be provided in a separate manual.~After 7 days on the assigned bucillamine dose and after providing the 24-hour urine sample, and after completing the Day 8 safety visit, subjects will undergo a 7 day washout where no CBTDs will be taken. Thereafter, subjects will be allowed to resume their originally prescribed CBTDs under Investigator's supervision.~One week following study drug discontinuation, subjects will return to the clinic for follow-up safety assessments.
Subjects on a standard regimen of tiopronin (cystine binding thiol drug; CBTD) plus prescribed first-line therapy (i.e. on a hydration, alkali therapy and dietary restriction) who are failing therapy will be selected for this trial.~After completing informed consent, the subject will have Screening consisting of medication history and physical examination with vital signs. Samples of blood and urine will be taken for clinical laboratory and urinalysis. Patients will undergo a 12-lead ECG test. A history of side effects with current CBTD as well as laboratory recordings of abnormalities attributable to treatment will also be recorded.~Subjects will be dosed in a sequential manner, starting with the low dose group (300 mg/day), then proceeding to the 600 mg.day dose group.. Safety and tolerability will be monitored closely by an Independent Medical Monitor (IMM) and based on the IMM's assessment that it is safe to proceed to the higher dose (600 mg/day), subsequent subjects will be enrolled into that group. Up to 15 subjects each will be enrolled into either Group A or Group B.~After 7 days on the assigned bucillamine dose, a 24-hour urine sample will be taken and after completing the Day 8 safety visit, subjects will undergo a 7 day washout where no CBTDs will be taken. Thereafter, subjects will be allowed to resume their originally prescribed CBTDs under Investigator's supervision.~One week following study drug discontinuation, subjects will return to the clinic for follow-up safety assessments.