A phase 1, open-label, drug-drug interaction study to evaluate the effect of multiple doses of tigulixostat on the pharmacokinetics of single-dose theophylline in healthy adult volunteers.

Inclusion Criteria:

• Male or female, Ages 18 to 55, inclusive.
• BMI 18.0 - 32.0 kg/m2, inclusive, at screening.
• In good general health as determined by medical history, clinical laboratory assessments, vital sign measurements, 12-lead ECG results, and physical examination findings at screening.
• Females of childbearing potential and males who agree to use contraception. Non-pregnant, non-lactating females who must have a negative pregnancy test at screening and check-in.

Exclusion Criteria:

• Significant history or indications of ill-health, as judged by the investigator.
• Any surgical or medical condition(s) possibly affecting drug absorption, distribution, metabolism, and excretion.
• eGFRcr of <60 (mL/min)/1.73 m2 at screening.
• alanine aminotransferase, aspartate aminotransferase, or total bilirubin ≥2 times the upper limit of normal at screening and check-in.
• Used any prescription or over-the-counter medications (except acetaminophen [Tylenol] up to 2 g per day), including herbal or nutritional supplements, within 14 days before the first dose of study drug.
• Consumed grapefruit or grapefruit juice, Seville orange or Seville orange-containing products (eg, marmalade), or caffeine- or xanthine-containing products within 48 hours before the first dose of study drug.
• History of hypersensitivity to theophylline or other xanthines and tigulixostat.