Clinical Trial of All-trans-retinoic Acid, Bevacizumab and Atezolizumab in Colorectal Cancer

Inclusion Criteria:

1. Histologically proven stage IV colon adenocarcinoma (any T [Tx, T1, T2, T3, or T4],N1- 2, M1). Tumors must be deemed to originate in the colon including tumors thatextend into/involve the small bowel (e.g. those at the ileocecal valve).

2. Known DNA mismatch repair or microsatellite instability status. Only one of thesetests is required for enrollment as there is 95% concordance rate of these tests.

• The eligible patient's tumors be classified as proficient in DNA mismatchrepair (pMMR) by immunohistochemistry (IHC) for MMR protein expression (MLH1,MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), PMS2. Tumors with intactexpression of all MMR proteins will be considered pMMR.

• OR

• The eligible patient's tumor be classified by Pathologic Complete Response (pCR) as stable microsatellite stability status (MSS) for panel ofmicrosatellite markers, OR

• MSS by commercially available next generation sequencing testing. OR

• If tumor-based test are not feasible, then commercially available circulatingtumor DNA tests showing MSS status will also be acceptable.

3. The patients should have received at least two lines of systemic chemotherapies inmetastatic setting. They should have received fluoropyrimidine, irinotecan, andoxaliplatin unless medically contraindicated. Prior anti-VEGF (vascular endothelialgrowth factor) therapy is accepted for enrollment since anti-VEGF therapy maintainsits benefit across several lines of therapy. If clinically appropriate, the patientsshould have received anti-EGFR (epidermal growth factor receptor) therapy for allRat sarcoma (RAS) wild type colorectal cancers and v-raf murine sarcoma viraloncogene homolog B1 (BRAF) V600E mutation-directed therapy for BRAF V600E mutantcolorectal cancers and HER2 targeted therapy for HER2 amplified colorectal cancers.

4. Age 18 and above

5. Performance status Eastern Cooperative Oncology Group (ECOG) 0-2

6. Adequate organ and marrow function

• Hemoglobin ≥ 9.0 g/dL

• Lymphocyte count > 0.5 x 109/L (500/uL)

• Absolute Neutrophil Count (ANC) ≥ 1500 mm3

• Platelet Count ≥ 100,000 mm3

• Creatinine ≤ 1.5 x upper limit of normal or Calculated Creatinine Clearance ≥ 45 mL/min

• Total Bilirubin ≤ 1.5 x upper limit of normal unless Gilbert syndrome with thefollowing exception: Patients with known Gilbert disease: serum bilirubin >3ULN

• Aspartate Aminotransferase (AST) / Alanine Aminotransferase (ALT) ≤ 2.5 x upperlimit of normal

• The subject's urinary protein is < 1+ on dipstick or routine urinalysis; ifurine protein (which is equal to 30 mg/dL on random urine protein assessment);if urine protein is ≥ 2+ (equal to 100mg/dL on random urine proteinassessment), a 24-hour urine must be collected and must demonstrate < 1000 mgof protein in 24 hours to allow participation in the study.

• Serum albumin ≥ 25 g/L (2.5 g/dL)

7. Negative HIV testing at screening, with following exception: patients with positiveHIV tests at screening are eligible provided they are stable on anti-retroviraltherapy, have a cluster of differentiation 4 (CD4) count > 200/uL, and haveundetectable viral load.

8. Negative hepatitis B surface antigen (HBsAg) test at screening. If a prior testingis available within previous 12 months and negative, this criteria can be consideredto be met.

9. Ability to understand and the willingness to sign a written informed consent

10. All men, as well as women of child-bearing potential must agree to use adequatecontraception (hormonal or barrier method of birth control with <1% failure rate,tubal ligation, male sterilization; abstinence) prior to study entry, for theduration of study participation, and for 6 months following completion of therapy.Women must refrain from donating eggs during this same period. Should a woman becomepregnant or suspect she is pregnant while participating in this study, she shouldinform her treating physician immediately.

11. A female of child-bearing potential is any woman (regardless of sexual orientation,marital status, having undergone a tubal ligation, or remaining celibate by choice)who meets the following criteria: Has not undergone a hysterectomy or bilateraloophorectomy; or has not been naturally postmenopausal for at least 12 consecutivemonths (i.e. has had menses at any time in the preceding 12 consecutive months).

12. Negative hepatitis C virus (HCV) antibody test at screening, or positive HCVantibody test followed by a negative HCV RNA test at screening The HCV RNA test mustbe performed for patients who have a positive HCV antibody test. If a prior testingis available within previous 12 months and negative, this criteria can be consideredto be met.

Exclusion Criteria:

1. Microsatellite unstable colorectal (MSI-H) cancers identified by PCR testing OR bycommercially available Next-generation sequencing (NGS) and Circulating tumor DNA (ctDNA) testing OR by loss of expression of one or more of the MMR enzymes (MLH1,MSH2, MSH6, PMS2) on immunohistochemistry. Only one such test is required to confirmeligibility.

2. Current active known or suspected autoimmune disease such as including colitis,inflammatory bowel disease (i.e. ulcerative colitis or Crohn's disease), rheumatoidarthritis, pan-hypopituitarism, History of idiopathic pulmonary fibrosis, organizingpneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, or idiopathicpneumonitis, or evidence of active pneumonitis on screening chest computedtomography (CT) scan, adrenal insufficiency treated with immunosuppressive steroidsand biologics treatment. Patients with controlled disease with no active treatmentor prednisone < 10 mg daily may be eligible based on treating physician assessment. Participants with vitiligo, type I diabetes mellitus, residual hypothyroidism due toautoimmune condition only requiring hormone replacement, psoriasis not requiringsystemic treatment, history of radiation pneumonitis in the radiation field (fibrosis) is permitted or conditions not expected to recur in the absence of anexternal trigger are permitted to enroll.

3. Any condition requiring systemic treatment with either corticosteroids (> 10 mgdaily prednisone equivalent) or other immunosuppressive medications within 14 daysprior to the first dose of study drug. Inhaled steroids and adrenal replacementsteroid doses up to 10 mg daily prednisone equivalent are permitted (although notencouraged) in the absence of active autoimmune disease.

4. Prior use of atezolizumab or ATRA is not eligible. Prior use of any otherimmunotherapy such anti programmed death-ligand 1 (PD-L1), anti- programmed celldeath protein 1 (PD-1), Anti-CTLA4 will also be excluded.

5. Chemotherapy, radiotherapy, or other cancer therapy within 3 weeks prior to startingstudy treatment.

6. Subjects must have recovered from prior treatment-related to toxicities to grade 1or baseline (excluding alopecia and clinically stable toxicities requiring ongoingmedical management, such as hypothyroidism from prior immune checkpoint inhibitortreatment).

7. Subjects may not be receiving any other investigational agents for the treatment ofthe cancer under study within 28 days prior to initiation of study treatment

8. Untreated brain metastases are not allowed. If prior treatment of brain metastaseswith surgery and/or radiation therapy has been provided, those patients will beclinically stable and not requiring escalating doses of steroids.

9. History of allergic reactions attributed to compounds of similar chemical orbiologic composition to ATRA, atezolizumab, and bevacizumab or other agents used instudy.

10. Inadequately controlled hypertension (defined as systolic blood pressure >150 mmHgand/or diastolic blood pressure >100 mmHg), history of hypertensive crisis orhypertensive encephalopathy. Clinically significant cardiovascular disease, such ascerebrovascular accident within six months prior to enrollment, myocardialinfarction within six months of prior to enrollment, unstable angina History ofhypertensive crisis or hypertensive encephalopathy. If patient has previouslyreceived bevacizumab safely after that episode, with adequate BP control, thenpatients will be eligible.

11. Uncontrolled inter current illness including, but not limited to, ongoing or severeinfection within 4 weeks prior to initiation of study treatment that could impactpatient safety, symptomatic congestive heart failure with reduced ejection fractionhistory and the New York Heart Association (NYHA) Functional Classification classIII or IV, cardiac arrhythmia, or psychiatric illness/social situations that, in theopinion of the investigator, would limit compliance with study requirements.

12. Subjects must not be pregnant or nursing due to the potential for congenitalabnormalities and the potential of this regimen to harm nursing infants. orbreastfeeding, or intention of becoming pregnant during study treatment or within 5months for atezolizumab and 6 month for bevacizumab after the final dose of studytreatment. Women of childbearing potential must have a negative serum pregnancy test resultwithin 14 days prior to initiation of study treatment

13. History of leptomeningeal disease or un-controlled tumor related pain. Patientrequiring pain medications should be on a stable regimen. Symptomatic lesions (e.g.bone metastasis or metastasis causing nerve impingement) amenable to radiationtherapy should be treated before enrollment and patient should have recovered fromthat radiation. No required minimum recovery period from the radiation.

14. Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to initiationof study treatment. Patients receiving prophylactic antibiotics (e.g., to prevent aurinary tract infection or chronic obstructive pulmonary disease exacerbation) areeligible for the study

15. Prior allogeneic stem cell or solid organ transplantation

16. Treatment with a live, attenuated vaccine within 4 weeks prior to initiation ofstudy treatment, or anticipation of need for such a vaccine during atezolizumabtreatment or within 5 months after the final dose of atezolizumab

17. History of Grade 4 venous thromboembolism. If previously have received bevacizumabsafely after that episode then patients will be eligible

18. History of Grade > 2 hemoptysis (defined as > 2.5 mL of bright red blood perepisode) within 1 month prior to screening

19. History or evidence of inherited bleeding diathesis or significant coagulopathy atrisk of bleeding (i.e., in the absence of therapeutic anticoagulation)

20. Currently active abdominal fistula, GI perforation, intra-abdominal abscess, oractive GI bleeding requiring transfusion of blood products or hospitalization within 6 months

21. Serious, non-healing wound, active non-healing ulcer, or untreated bone fracture

22. Major surgical procedure, other than for diagnosis, within 4 weeks prior toinitiation of study treatment, or anticipation of need for a major surgicalprocedure during the study

23. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrentdrainage procedures (once monthly or more frequently). Patients with indwellingcatheters (e.g., PleurX) are allowed.

24. Uncontrolled or symptomatic hypercalcemia (ionized calcium >1.5 mmol/L, calcium >12mg/dL or corrected serum calcium >ULN)

25. Any other disease, metabolic dysfunction, physical examination finding, or clinicallaboratory finding that contraindicates the use of an investigational drug, mayaffect the interpretation of the results, or may render the patient at high riskfrom treatment complications

26. Treatment with systemic immunostimulatory agents (including, but not limited to,interferon and interleukin 2 [IL-2]) within 4 weeks or 5 half-lives of the drug (whichever is longer) prior to initiation of study treatment

27. Known active hepatitis B or C, active tuberculosis and known uncontrolled HIV