This phase II trial compares the effect of usual treatment approach alone (FOLFOX or CAPOX after chemoradiation) with using FOLFIRINOX after chemoradiation in patients with stage II-III rectal cancer. Combination chemotherapy regiments, such as FOLFIRINOX [folinic acid (leucovorin), fluorouracil, irinotecan, and oxaliplatin], FOLFOX (leucovorin, fluorouracil, and oxaliplatin), or CAPOX (capecitabin and oxaliplatin) use more than one anticancer drug that work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. FOLFOX or CAPOX are used after chemoradiation as usual treatment for rectal cancer. Giving FOLFIRINOX after chemoradiation may increase the response rate for the primary rectal tumor and lead to higher rates of clinical complete response (and thus a chance to avoid surgery) compared to FOLFOX or CAPOX after chemoradiation in patients with locally advanced rectal cancer.

The PIK3CA gene is frequently mutated in breast cancer, leading to disease aggressiveness and
patient mortality. Alpelisib, a small molecule that inhibits the activity of the PIK3CA gene
product PI3K, has demonstrated clinical benefit in cancer patients with this gene mutation.
However, hyperglycemia, an on-target toxicity associated with alpelisib that leads to
hyperinsulinemia, limits the drug's clinical efficacy and induces high grade hyperglycemia in
patients with baseline metabolic dysfunction, insulin resistance and/or elevated HbA1c.
Restoring insulin sensitivity and reduction in circulating concentrations of insulin have
been reported to improve the activity of alpelisib.

Evexomostat (SDX-7320) is a polymer-conjugate of a novel small molecule methionine
aminopeptidase 2 (MetAP2) inhibitor that has demonstrated the ability to reduce
alpelisib-induced hyperglycemia in multiple animal experiments and has demonstrated
synergistic anti-tumor activity independent of changes in glucose or insulin. Evexomostat was
well tolerated in a Phase 1 safety study in late-stage cancer patients and showed
improvements in insulin resistance for patients that presented with baseline elevated
insulin. Overall, the most common treatment-emergent adverse events with evexomostat (TEAEs)
were fatigue (44%), decreased appetite (38%), constipation and nausea (each 28%), and
diarrhea (22%). All other TEAEs occurred at an incidence <20%.

The purpose of this study is to characterize the safety of the triplet drug combination
(alpelisib, fulvestrant plus evexomostat), to test whether evexomostat, when given in
combination with alpelisib and fulvestrant will reduce the number and severity of
hyperglycemic events and/or reduce the number of anti-diabetic medications needed to control
the hyperglycemia for patients deemed at risk for alpelisib-induced hyperglycemia (baseline
elevated HbA1c or well-controlled type 2 diabetes), and to assess preliminary anti-tumor
efficacy and changes in key biomarkers and quality of life in this patient population.