A Phase 1, Randomized, Placebo-Controlled, Double-Blind, Sponsor-Open Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of TAK-781 in Healthy Participants and a Single-Arm, Open-Label Evaluation in Participants With Non-Cirrhotic Primary Sclerosing Cholangitis
The main aim of this study is to see if the drug TAK-781 is safe for healthy volunteers and for participants with PSC. The study will also look at how well participants can tolerate TAK-781. In addition, the study will check how the body absorbs, uses, and gets rid of TAK-781 (Pharmacokinetics \[PK\]), how the drug affects the body (Pharmacodynamics \[PD\]), and how the body's immune system reacts to TAK-781 (Immunogenicity). The study consists of two phases (Phase 1a and 1b). Phase 1a includes two parts: Part 1 (Single Ascending Dose \[SAD\]) and Part 2 (Multiple Ascending Dose \[MAD\]). In Part 1, healthy participants will receive either single dose of TAK-781 or a placebo. A placebo looks the same as TAK-781 but has no medicine in it. In Part 2, healthy participants will receive multiple doses of TAK-781 or a placebo. In Phase 1b (Part 3), participants with large duct, non-cirrhotic PSC will receive a single dose of TAK-781. Participants will be in the study for about 36 weeks.
• The participant is willing and able to fully comply with all trial procedures and requirements, in the investigator's opinion.
• The participant has provided informed consent (that is, in writing, documented via a signed and dated informed consent form (ICF) or electronic consent \[e-consent\] if applicable) and any required privacy authorization prior to the initiation of any trial procedures.
• Male at birth and female at birth participants aged 18 to 68 years, inclusive, at the time of consent.
• The participant is judged to be in good health (for example, no evidence of cardiovascular, liver, metabolic, gastroenterological, or kidney disease) by the investigator, based on clinical evaluations including laboratory safety tests, medical history, physical examination, ECG, and vital sign measurements performed at the first screening visit.
• The participant must have a body mass index (BMI) of less than 30.0 kilograms per square meter (kg/m\^2) at the time of screening.
• Has not had frequent or heavy use (that is, near-daily) of medical or recreational cannabis for at least 3 months before screening.
• The participant must not be a person of childbearing potential (POCBP) defined by at least 1 of the following criteria:
‣ Surgically sterile for at least 6 weeks at screening (defined as having undergone one of the following procedures: hysterectomy, bilateral oophorectomy, or bilateral salpingectomy).
⁃ Postmenopausal at screening (defined as no menses for 12 months without an alternative medical cause). A high follicle-stimulating hormone (FSH) level (greater than or equal to \[\>=\]40 international units/liter \[IU/L\] in the postmenopausal range may be used to confirm a postmenopausal state in women not using hormonal contraception or hormonal replacement therapy. However, in the absence of 12 months of amenorrhea, a single FSH measurement is insufficient.
⁃ Has no uterus as a result of congenital condition. The participant must not donate ova for at least 6 months after the last dose of trial intervention.
• Male participants (based on sex at birth) must use highly effective contraception, from the date of signing the ICF, throughout the duration of the trial, and for 6 months after the last dose of trial intervention. The participant must not donate sperm for at least 6 months after the last dose of trial intervention.
• The participant is willing and able to fully comply with all trial procedures and requirements, in the investigator's opinion.
• The participant has provided informed consent (that is, in writing, documented via a signed and dated ICF or e-consent if applicable) and any required privacy authorization prior to the initiation of any trial procedures.
• Male at birth and female at birth participants aged 18 to 68 years, inclusive, at the time of consent.
• Confirmed diagnosis of large-duct PSC based on any 2 of the following 3 criteria:
‣ Historical evidence of an elevated alkaline phosphatase (ALP) greater than \[\>\] upper limit of normal (ULN) from any laboratory.
⁃ Historical liver biopsy with histologic features consistent with large-duct PSC, in the appropriate clinical context (such as cholestatic liver enzyme profile, inflammatory bowel disease \[IBD\] history).
⁃ Historical abnormal cholangiography consistent with PSC as measured by magnetic resonance cholangiopancreatography (MRCP), endoscopic retrograde cholangiopancreatography, or percutaneous transhepatic cholangiography.
• The participants must have a fibrogenesis biomarker over pre-defined level.
• The participants must have evidence for moderate/advanced fibrosis but not cirrhosis as defined by enhanced liver fibrosis (ELF) \>= 7.7 but less than or equal to (\<=) 11.3 at Visit 1.
• No evidence of cholangiocarcinoma or any other malignancy on magnetic resonance imaging (MRI) at screening.
• Participants with a certain concomitant disease are allowed to enroll if pre-defined criteria are met.
• Participants must have certain additional laboratory parameters in specified ranges at screening.
⁃ Has not had frequent or heavy use (that is, near-daily) of medical or recreational cannabis for at least 3 months before screening.
⁃ A female and male participant (based on sex at birth) must use highly effective contraception, from the date of signing the ICF, throughout the duration of the trial, and for 6 months after the last dose of trial intervention. The participant must not donate ova or sperm for at least 6 months after the last dose of trial intervention.
⁃ A POCBP must have a negative serum pregnancy test at first screening visit and urine pregnancy test on second screening visit and Day 1 before dosing.
⁃ Participants must be able to be educated regarding the correct process/procedure, verbally state understanding and comply with the correct process/procedure of the administration SC investigational product (IP) for the duration of the trial.