The Purpose of This Trial is to Determine if Regorafenib Plus Durvalumab (MEDI4736) is Safe and Effective in Treatment of Chemo Refractory Advanced Biliary Tract Cancers

Inclusion Criteria:

• Ability of patient OR Legally Authorized Representative (LAR) to understand thisstudy, and participant or LAR willingness to sign a written informed consent

• Can swallow tablets and self-administer medication

• Progressed on at least one line of therapy (no restrictions on type of previoustreatment)

• Eastern Cooperative Oncology Group (ECOG) Performance Status = 0 - 1

• Measurable disease with at least 1 lesion that qualifies as a RECIST 1.1 TargetLesion (TL) at baseline. Previously irradiated lesion cannot be considered as TargetLesion (TL) except in cases of documented progression of the lesion since thecompletion of radiation therapy

• Histologically confirmed unresectable or metastatic intrahepatic/extrahepaticcholangiocarcinoma or gallbladder cancer with radiographic progression, who haveprogressed on one line of therapy / failed adjuvant therapy

• Life expectancy of at least 3 months

• Recovery to baseline or < Grade 2 CTCAE v5.0 from toxicities related to any priortreatments, unless adverse event's (AE(s)) are clinically nonsignificant and/orstable on supportive therapy

• Adequate organ function per laboratory results

• Concomitant anticoagulation with oral anticoagulants (e.g., warfarin, directthrombin and Factor Xa inhibitors) or platelet inhibitors (e.g., clopidogrel) willbe allowed provided that no prior evidence of underlying abnormality in coagulationparameters exists. Close monitoring of at least weekly evaluations will be performeduntil international normalized ratio/ partial thromboplastin time (INR/PTT) isstable based on a measurement that is pre-dose as defined by the local standard ofcare

• Weight > 30 kg (66 lbs)

• Women of child-bearing potential and men with partners of child-bearing potentialmust agree to use an acceptable form of contraception for the duration of studyparticipation, and for 7 months after the last study treatment

• Men of child-bearing potential must agree not to donate sperm while on this studyand for 180 days (6 months) after the last dose of study treatment

Exclusion Criteria:

• Current or anticipated use of other investigational agents while participating inanother clinical study, unless it is an observational (noninterventional) clinicalstudy or during the follow-up period of an interventional study

• Psychiatric illness/social situations that would limit compliance with studyrequirements

• Pregnant or breastfeeding

• Ampullary carcinoma

• Previous treatment with regorafenib

• Previous treatment with a programmed death 1 (PD1), programmed death-ligand (PD-L1,including durvalumab), or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)inhibitors, or agent directed to another co-inhibitory T cell receptor

• Previous treatment with live vaccine within 30 days of planned start of study drugs (seasonal flu vaccines that do not contain a live virus are permitted)

• Active autoimmune disease (active defined as having autoimmune disease relatedsymptoms and detectable autoantibodies) that has required systemic treatment in thepast 2 years

• Diagnosis of immunodeficiency or receiving chronic systemic steroid therapy or anyother form of immunosuppressive therapy within 7 days prior to the first dose ofstudy drugs. Except Intranasal, inhaled, topical steroids, or local steroidinjections (e.g., intra articular injection), systemic corticosteroids atphysiologic doses not to exceed 10 mg/day of prednisone or its equivalent, steroidsas premedication for hypersensitivity reactions (e.g., CT scan premedication)

• Known history of human immunodeficiency virus (HIV) infection (HIV 1/2 antibodies).Dual active hepatitis B virus (HBV) infection (HBsAg (+) and /or detectable HBV DNA)and HCV infection (anti-HCV Ab(+) and detectable HCV RNA) at study entry. Singleactive infection of HBV or HCV infection is allowed with treatment by localstandards

• Has untreated central nervous system (CNS) metastases and/or carcinomatousmeningitis identified either on the baseline brain imaging, unless known and treatedwith stable for >4 weeks

• Significant acute gastrointestinal disorders with diarrhea as a major symptom e.g.,Crohn's disease, malabsorption, or CTCAE Grade ≥ 2 diarrhea of any etiology

• Receipt of the last dose of anticancer therapy (chemotherapy, immunotherapy,endocrine therapy, targeted therapy, biologic therapy, tumor embolization,monoclonal antibodies) ≤ 21 days prior to the first dose of study drug

• Any concurrent chemotherapy, investigational product (IP), biologic, or hormonaltherapy for cancer treatment. Concurrent use of hormonal therapy fornon-cancer-related conditions (e.g., hormone replacement therapy) is acceptable.However, the palliative radiation to non-targeted lesions is allowed

• Abdominal fistula, GI perforation, bowel obstruction, or intra-abdominal abscesswithin 8 weeks before first dose. Note: Complete healing of an intra-abdominalabscess must be confirmed before first dose

• Uncontrollable ascites or pleural effusion

• Clinically significant gross hematuria, hematemesis, or hemoptysis of >0.5 tsp (2.5ml) of red blood, or other history of grade 3 significant bleeding within 8weeks

• Any unresolved toxicity NCI CTCAE v 5.0 Grade ≥2 from previous anticancer therapywith the exception of neuropathy grade 2 and below, alopecia, vitiligo, and thelaboratory values defined in the inclusion criteria

• Major surgery (e.g., GI surgery, removal or biopsy of brain metastasis) within 8weeks before first dose of study treatment. Complete wound healing from majorsurgery must have occurred 1 month before first dose and from minor surgery (e.g.,simple excision, tooth extraction) at least 10 days before first dose. Patients withclinically relevant ongoing complications from prior surgery are not eligible

• History of organ transplantation

• Uncontrolled intercurrent illness, including but not limited to, ongoing or activeinfection, symptomatic congestive heart failure, unstable angina pectoris, cardiacarrhythmia, interstitial lung disease

• Uncontrolled hypertension defined as sustained blood pressure (BP) > 150 mm Hgsystolic or > 100 mm Hg diastolic despite optimal antihypertensive treatment

• Mean QT interval corrected for heart rate (QTcF) >470 ms calculated from 3electrocardiograms (ECGs) (within 15 minutes at 5 minutes apart) using Fridericia'sCorrection

• Stroke (including transient ischemic attack transient ischemic attack (TIA),myocardial infarction (MI), or other ischemic event, or acute thromboembolic event (e.g., deep venous thrombosis, pulmonary embolism) that are NOT asymptomatic withlocal standard anti-coagulation within 4 weeks before first dose

• History of another primary malignancy in the last 3 years except:

• Malignancy treated with curative intent and with no known active disease ≥3years before the first dose of IP and of low potential risk for recurrence

• Adequately treated non-melanoma skin cancer or lentigo maligna without evidenceof disease

• Adequately treated carcinoma in situ without evidence of disease

• Use of any Herbal remedy

• Ongoing infection >grade 2

• Known allergy or hypersensitivity to any of the study drugs

• Proteinuria > Grade3 (>3.5g/24 hours)

• Active infection with tuberculosis (TB) (clinical evaluation that includes clinicalhistory, physical examination and radiographic findings, and TB testing in line withlocal practice)

• Participants with HBV infection (as characterized by positive hepatitis B surfaceantigen [HBsAg] and/or anti-hepatitis B core antibodies (anti-HBc) with detectableHBV deoxyribonucleic acid (DNA) [≥10 international units (IU)/mL or above the limitof detection per local laboratory]) must receive antiviral therapy prior torandomization to ensure adequate viral suppression

• Participants must remain on antiviral therapy for the study duration and for 6months after the last dose of study treatment. Participants who test positive foranti-HBc with undetectable HBV DNA (<10 IU/mL or under the limit of detection perlocal laboratory) do not require antiviral therapy unless HBV DNA exceeds 10IU/mL orreaches detectable limits per local laboratory during the course of treatment

• Patients positive for hepatitis C (HCV) antibody. EXCEPTIONS: Patients positive forhepatitis C (HCV) are eligible only if polymerase chain reaction is negative for HCVRNA.

Patients positive for hepatitis C (HCV) are eligible if they undergo treatment per local guidelines