A Study of RGX-202-01 With or Without FOLFIRI in Patients With Advanced Gastrointestinal Malignancies

Inclusion Criteria:

1. The patient must have histologic or cytologic evidence of a malignant gastrointestinal
tumor (gastric or gastroesophageal junction, pancreatic, biliary, small intestine, or
colorectal) of adenocarcinoma or poorly differentiated histology and must have disease
that is resistant to or relapsed following available standard systemic therapy or for
which there is no standard systemic therapy or reasonable therapy likely to result in
clinical benefit or if such therapy has been refused by the patient. Documentation of
the reason must be provided for patients who have not received a standard therapy
likely to result in clinical benefit.

2. The patient must have advanced disease, defined as cancer that is either metastatic or
locally advanced and unresectable (and for which additional radiation therapy or other
locoregional therapies are not considered feasible).

3. The patient must have disease that is measurable by standard imaging techniques by
RECIST version 1.1. For patients with prior radiation therapy, measurable lesions must
be outside of any prior radiation field(s), unless disease progression has been
documented at that disease site subsequent to radiation.

4. The patient is ≥18 years old.

5. The patient has an ECOG PS of ≤1.

6. The patient has adequate baseline organ function, as demonstrated by the following:

1. Serum creatinine ≤1.5 times institutional upper limit of normal (ULN) and
calculated creatinine clearance >50 mL/min;

2. Serum albumin ≥2.5 g/dl;

3. Bilirubin ≤1.5 × institutional ULN;

4. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 ×
institutional ULN; patients with hepatic metastases may have AST and ALT ≤ 5 ×
institutional ULN;

5. Absolute neutrophil count (ANC) ≥1.5×109/L;

6. Hemoglobin ≥8 g/dL and no red blood cell (RBC) transfusions during the prior 14
days;

7. Platelet count ≥100×109/L and no platelet transfusions during the prior 14 days.

7. For patients not taking warfarin: international normalized ratio (INR) ≤1.5 or
prothrombin time (PT) ≤1.5 × ULN; and either partial thromboplastin time or activated
partial thromboplastin time (PTT or aPTT) ≤1.5 × ULN. Patients on warfarin may be
included if on a stable dose with a therapeutic INR <3.5.

8. The patient has a left ventricular ejection fraction (LVEF) ≥ 45% as determined by
either echocardiography (ECHO) or multigated acquisition (MUGA) scanning.

9. If the patient is a woman of child bearing potential (WOCBP), she has had a negative
serum or urine pregnancy test within 2 weeks prior to treatment.

10. The patient (men and WOCBP) agrees to use acceptable contraceptive methods for the
duration of time on the study and continues to use acceptable contraceptive methods
for 1 month after the last dose of study therapy.

11. The patient has signed informed consent prior to initiation of any study-specific
procedures or treatment.

12. The patient is able to adhere to the study visit schedule and other protocol
requirements, including follow-up for survival assessment.

13. Patients with diabetes mellitus should be on a stable regimen of oral hypoglycemic
therapy and/or insulin before beginning study therapy with RGX-202-01 and serum
glucose values should consistently be grade 2 or less.

14. Tumor tissue (a minimum of 5 and up to 15 unstained slides, from a fresh tumor biopsy
prior to starting study therapy must be available prior to the first dose of study
therapy. This biopsy should be obtained within 28 days prior to starting RGX-202-01. A
biopsy obtained earlier than 28 days prior to start of RGX-202-01 may be considered
acceptable, especially if obtained within 3 months and if no systemic anti-cancer
therapy has been administered since the date of the biopsy. If a biopsy is deemed by
the investigator to not be feasible and/or in the patient's best interest, prior
approval must be obtained from the Medical Monitor to waive this requirement. In this
case, archived tumor tissue must be made available prior to commencing study
treatment.

Additional Inclusion Criteria for Expansion Stages:

1. For the single agent therapy expansion cohort, patients must have a gastrointestinal
malignancy expressing the CKB biomarker and must have received only one prior regimen
for advance/metastatic disease. Patients treated with more than one prior regimen must
be approved by the Medical Monitor. Only patients exhibiting positive expression of
CKB in tumor cells detected by an immunohistochemistry (IHC) method will be enrolled.

2. For the combination therapy expansion cohort, patients with gastroesophageal junction
or gastric cancer must have received only one prior systemic regimen in the metastatic
setting. Prior therapy with a checkpoint inhibitor (PD-1/PD-L1 inhibitor) is allowed
and patients may have received up to two prior regimens in the metastatic setting.

3. For the combination therapy expansion cohort, patients with colorectal cancer must
have have a tumor expressing the CKB biomarker by an immunohistochemistry (IHC)
method. Patients must have received at least one irinotecan-containing and one
oxaliplatin-containing regimen in the metastatic setting or have refused such therapy.
Patients with KRAS wild-type colorectal cancer must have received prior therapy with
cetuximab or panitumumab. Patients may have received up to two prior systemic regimens
in the metastatic setting. Patients with a Microsatellite Instability-High (MSI-High)
tumor must have received a checkpoint inhibitor (PD-1/PD-L1 inhibitor) and may have
received up to three prior systemic regimens in the metastatic setting. Patients may
have received prior treatment with bevacizumab.

Exclusion Criteria:

1. The patient has persistent clinically significant toxicities (Grade ≥2) from previous
anticancer therapy (excluding Grade 2 chemotherapy-related neuropathy and alopecia
which are permitted and excluding Grade 2-3 laboratory abnormalities if they are not
associated with symptoms, are not considered clinically significant by the
Investigator, or can be managed with available medical therapies).

2. The patient has a gastrointestinal malignancy of small cell, neuroendocrine, or
squamous histology.

3. The patient has received treatment with chemotherapy, external-beam radiation, or
other systemic anticancer therapy within 14 days prior to study therapy administration
(42 days for prior nitrosourea or mitomycin-C.

4. The patient has received treatment with an investigational systemic anticancer agent
within 5 half-lives of the investigational systemic therapy prior to study therapy
administration.

5. The patient has an additional active malignancy that may confound the assessment of
the study endpoints. Patients with a past cancer history with substantial potential
for recurrence must be discussed with the Medical Monitor before study entry. Patients
with the following concomitant neoplastic diagnoses are eligible: non-melanoma skin
cancer, carcinoma in situ (including transitional cell carcinoma, cervical
intraepithelial neoplasia, and melanoma in situ), organ-confined prostate cancer with
no evidence of progressive disease.

6. The patient has clinically significant cardiovascular disease (e.g., uncontrolled or
any New York Heart Association Class 3 or 4 congestive heart failure (see Appendix 1),
uncontrolled angina, history of myocardial infarction, unstable angina or stroke
within 6 months prior to study entry, uncontrolled hypertension or clinically
significant arrhythmias not controlled by medication).

7. The patient has known active or suspected brain or leptomeningeal metastases. Central
nervous system (CNS) imaging is not required prior to study entry unless there is a
clinical suspicion of CNS involvement.

8. The patient has uncontrolled intercurrent illness including, but not limited to,
uncontrolled infection, disseminated intravascular coagulation, or psychiatric
illness/social situations that would limit compliance with study requirements.

9. The patient is pregnant or breast feeding.

10. The patient has an ongoing chronic hepatopathy of any origin.

11. The patient has evidence of muscular dystrophies or ongoing muscle pathology.

12. The patient has oxygen-support requirements.

13. QTcF >450 msec (males) or >470 msec (females).

14. The patient has a physical abnormality or medical condition that limits swallowing
multiple pills or has a history of non-adherence to oral therapies.

15. The patient has a malabsorption condition, such as short bowel syndrome, impaired GI
function or GI disease that may significantly alter absorption, or a high likelihood
of impending bowel obstruction, such as strictures.

16. The patient has clinically significant ascites (i.e. requiring paracentesis within the
preceding 28 days or treatment with pain medication).

17. The patient has any medical condition which, in the opinion of the Investigator,
places the patient at an unacceptably high risk for toxicities.

The following exclusion criteria are relevant for patients who will be treated with
RGX-202-01 plus FOLFIRI, per protocol, on both Dose Escalation and Dose Expansion
Cohorts:

18. The patient has known dihydropyrimidine dehydrogenase (DPD) deficiency or is on
treatment with DPD inhibitors, including sorivudine or its chemically related
analogues such as brivudine, within 4 weeks prior to the start of FOLFIRI treatment.

19. The patient has a known prior history of severe myelosuppression, diarrhea, or
mucocutaneous toxicity with a 5FU- or irinotecan-containing regimen, or the patient is
known to be homozygous or heterozygous for the UGT1A1*28, UGT1A1*6, UGT1A9*1 or ABCG2
allele.

20. The patient requires treatment with strong CYP3A4 inhibitors or strong UGT1A1
inhibitors.

21. The patient has gastric/gastroesophageal junction, biliary, pancreatic, small bowel or
colorectal cancer and has previously received the FOLFIRI regimen at any point in the
past with evidence of disease progression within 8 weeks of starting FOLFIRI.