DRP-104 (Glutamine Antagonist) in Combination With Durvalumab in Patients With Advanced Stage Fibrolamellar Carcinoma (FLC)

Inclusion Criteria: * Must have histologically confirmed FLC (Fibrolamellar Carcinoma) that is metastatic or unresectable. * Presence of DNAJB1-PRKACA fusion transcript, assessed by RNA-sequencing, DNA-sequencing, or in situ hybridization in the archival tissue. * Must have demonstrated radiographic progression on prior or current immunotherapy. * Age ≥ 12 years. * Patients \< 18 years old must have a body weight ≥ 40 kg. * Eastern Cooperative Oncology Group (ECOG) performance status of ≤2 * Patients must have adequate organ and marrow function defined by study-specified laboratory tests. * Patients must have adequate kidney and liver function defined by study-specified laboratory tests. * Must have measurable disease per RECIST 1.1 * Willingness to provide tissue and blood samples for mandatory translational research. * Women of childbearing potential (WOCBP) must have a negative urine or serum pregnancy test. * For both Women and Men, must use acceptable form of birth control while on study. * Ability to understand and willingness to sign a written informed consent document. Exclusion Criteria: * Must have had chemotherapy or other systemic therapy or radiotherapy, as follows: * Patients who have had chemotherapy, biological cancer therapy, or radiation 21 days prior to the first dose of study drug. * Patients who have had surgery within 28 days of dosing of investigational agent, excluding minor procedures. * Patients who have received other approved or investigational agents or device within 21 days of the first dose of study drug. * Patients who have not recovered from acute adverse events to grade ≤1 or baseline due to agents administered, with exception of grade 2 fatigue, rash, and endocrinopathy successfully managed hormone replacement therapy, or alopecia or stable neuropathy, unless approved by the investigational new drug (IND) Sponsor. * Patients with corrected QT interval (QTc) prolongation \> 470 ms according to Fridericia formula. * Patients receiving potent inducers of Cytochrome P450 3A (CYP 3A4/5) (including apalutamide, carbamazepine, enzalutamide, mitotane, phenytoin, rifampin and St. John's Wort) that cannot be discontinued at least 14 days prior to Cycle 1 Day 1. * Known sensitivity to or history of allergic reactions attributed to compounds of similar chemical or biologic composition of DRP-104 or durvalumab. * Subjects with interstitial lung disease that is symptomatic or may interfere with the detection or management of suspected drug-related pulmonary toxicity. * Has a pulse oximetry of \<92% on room air or is on supplemental home oxygen. * Active or untreated brain metastases or leptomeningeal metastases. * Uncontrolled intercurrent active medical and/or psychiatric illness/social psychosocial problems that that would limit compliance with study requirements. * Uncontrolled intercurrent illness including, but not limited to, uncontrolled infection, symptomatic congestive heart failure, unstable angina, cardiac arrhythmia, metastatic cancer, or psychiatric illness/social situations that would limit compliance with study requirements. * Pregnant or breastfeeding. * Has a known history of Human Immunodeficiency Virus (HIV)/AIDS. * Has active hepatitis B. Patients with chronic or acute hepatitis B virus (HBV) infection . * Have had evidence of active or acute diverticulitis, intra-abdominal abscess, or GI obstruction which are known risk factors for bowel perforation should be evaluated for the potential need for additional treatment before coming on study. * Patient is unwilling or unable to follow the study schedule for any reason. * Patient is at the time of signing informed consent a regular user (including "recreational use") of any illicit drugs or had a recent history (within the last year) of substance abuse (including alcohol). * Evidence of clinical ascites. * Participants a with history of prior unacceptable and/or life-threatening toxicities attributed to anti-programmed death-receptor 1 (PD1) or anti-PD-L1 (anti-programmed death-receptor 1) therapy. * Has active autoimmune disease that has required systemic treatment in the past 2 years. * Prior allogeneic stem cell transplantation or organ transplantation. * Has a diagnosis of immunodeficiency. * Systemic corticosteroids at immunosuppressive doses. * Patients who have had either of the following procedures or medications within 4 weeks prior to initiation of study treatment: * Any live, attenuated vaccine * Allergen hypo sensitization therapy in the last 2 weeks