Inclusion Criteria:

• Age ≥ 18 years
• Histologically/cytologically confirmed biliary tract cancer.
• Advanced or metastatic disease that is refractory to gemcitabine or fluoropyrimidine based therapy, or if there is intolerance to these regimens.
• Measurable disease by RECIST v1.1.
• Hemoglobin > 8 mg/dL.
• Absolute neutrophil count (ANC) > 1000/microL.
• Platelet count > 100,000/microL.
• Aspartate aminotransferase (AST) < 5 x upper limit of normal (ULN).
• Alanine aminotransferase (ALT) < 5 x ULN.
• Total bilirubin < 1.5 x ULN.
• Serum creatinine clearance > 50 mg/ml by Cockcroft-Gault formula.
• Creatinine clearance for males = (140 - age) (weight in kg)(72) (serum creatinine in mg/dL).
• Creatinine clearance for females = (140 - age) (weight in kg) (0.85)(72) (serum creatinine in mg/dL).
• Eastern Cooperative Oncology Group (ECOG) performance score 0-1.

Exclusion Criteria:

• Pregnant or breast-feeding.
• Female patients who can become pregnant and do not agree to use 2 forms of contraception (1 effective form plus a barrier method [oral, injected or implanted hormonal contraception and condom; intra-uterine device and condom; diaphragm with spermicidal gel and condom]) or to sexual abstinence, effective from the first administration of NXP800, throughout the trial and for six months afterwards.
• Male patients with partners of child-bearing potential who do not agree to take measures not to father children by using a barrier method of contraception (condom plus spermicide) or to sexual abstinence effective from the first administration of NXP800, throughout the trial and for six months afterwards. Men with pregnant or lactating partners must be advised to use barrier method contraception to prevent exposure of the fetus or neonate.
• Uncontrolled infection.
• Presence of another primary malignancy not in remission.
• New York Heart Classification 3 or greater heart failure.
• Uncontrolled brain metastatic disease.
• Systemic anti-neoplastic therapy or radiation therapy within 14 days of administration of NXP800.
• Usage of drugs that strongly inhibit or induce CYP3A4 for 1 week prior to starting NXP800 and for the duration of NXP800 dosing. Drugs that are low, medium, or other inhibitors of CYP3A4 are not prohibited and should be used with caution. Drugs that inhibit BCRP are not prohibited but should be used with caution, since NXP800 was found to be a BCRP substrate.
• Usage of seville oranges, grapefruit or grapefruit juice or products for 1 week prior to starting NXP800 and for the duration of NXP800 dosing.
• Surgical procedure within 30 days of administration of NXP800.
• Unwillingness to follow study related procedures.
• Inability to provide informed consent.

Eligibility last updated 7/19/23. Questions regarding updates should be directed to the study team contact.