Background: Melphalan, remains the mainstay of conditioning for autologous hematopoietic stem cell transplantation (HSCT) in multiple myeloma (MM) and non-Hodgkin lymphoma (NHL) patients. Gastrointestinal symptoms represent the most significant non-hematologic toxicities following high-dose melphalan conditioning, with approximately 40% of patients experiencing CTCAE grade 2 or higher diarrhea following conditioning regimens containing melphalan. Enterade is a proprietary blend of electrolytes and five amino-acids that can facilitate retention of the absorbing capacity of the small intestine by rebuilding the villi and reduce antigenic translocation by tightening the mucosal barrier. In a study of irradiated mice, enterade improved survival and improved body weight following irradiation. The goal was to investigate the effectiveness of enterade to reduce GI toxicities after high-dose melphalan chemotherapy. Methods: The trial was designed as a Phase 2, multi-center, double-blinded, 2-arm randomized study. 114 MM or NHL patients were enrolled between October 2016 and October 2017. Patients received either two 8oz bottles/day of enterade or placebo starting on the day of admission through Day +14. GI toxicity was scored by the CT-CAE 4.0 system from admission through Day + 14. Compliance was arbitrarily set at consumption of 2 bottles daily for 11+ days. Results: Of the 114 enrolled patients, 99 (61 MM, 38 NHL) attempted to consume at least 1 dose of enterade/placebo. Compliance overall was much lower than anticipated; with no MM patients achieving compliance compared to 34.2% in the NHL group. Compliance in NHL patients was 31.6% in the enterade group versus 36.8% in the placebo group. Analysis of primary endpoint in NHL patients showed a 16% incidence of diarrhea ≥ grade 2 in enterade compliant patients versus 86% in the placebo group (p= 0.02). Conclusions: Eleven days of two 8oz bottles of liquid is a difficult task during ASCT, especially for MM with nausea, altered taste and poor appetite. For those NHL patients, compliant per protocol (who consumed ≥11 days), enterade significantly reduced diarrhea. The use of enterade to prevent diarrhea following high-dose chemotherapy should be explored further in populations capable of reasonable oral intake. Clinical trial information: NCT02919670