Abstract PO3-13-01: ONTARGET: Phase 3 randomized, double-blind, placebo-controlled trial evaluating crofelemer for the prophylaxis of diarrhea in adult patients with solid tumors receiving targeted therapies with or without standard chemotherapy
Authors: Schwartzberg Lee , Okhuysen Pablo , Roeland Eric , Vidal Gregory , Harnden Kathleen , Zuniga Richard , Bosnjak Snezana , Daggubati Sreedevi , Bursac Daliborka 
Published: May 2024

Background: Cancer therapy-related diarrhea (CTD) can result in fluid and electrolyte losses, malnutrition, unexpected hospitalization, and poor quality of life (QoL) of patients with cancer. CTD can also limit response to cancer therapy due to treatment interruption, discontinuations, or dose modifications. CTD is a common side effect of targeted therapies (TTx) (e.g., inhibitors of tyrosine kinases, EGFR, CDK4/6, VEGFR) with or without concomitant chemotherapy (ChemoRx) for treating various solid tumors, including breast cancer (BRCA). TTx induce CTD by increasing intracellular cAMP or Ca++ leading to activation of two intestinal Cl- channels, CFTR and CaCC, increasing luminal secretion of Cl- and accompanying loss of Na+ and fluids. For most patients with cancer, CTD management with dietary modifications and antimotility agents is suboptimal. New drugs are needed to prevent or mitigate CTD, a huge unmet medical need.

Since the mechanism of CTD is mostly secretory, we hypothesized that crofelemer (CRO) an oral botanical drug purified from the latex of the Croton lechleri tree that modulates both intestinal Cl- ion channels, CFTR and CaCC, may benefit preventing CTD. CRO is negligibly absorbed orally and is FDA-approved for symptomatic relief of noninfectious diarrhea in adults with HIV/AIDS on antiretroviral therapy. In a phase 2 study in 51 women with BRCA receiving THP/TCHP (HALT-D), CRO given daily, compared to standard of care (SOC), for 2 cycles resulted in grade ≥2 diarrhea in significantly fewer subjects (9.0% vs. 33.3%, p=0.0361) in cycle 2 and was 1.8 times more likely to resolve diarrhea (p=0.0425) (Pohlmann et al. 2022; NCT02910219)

Methods: ONTARGET (NCT04538625) is a randomized, multicenter, international, double-blind, placebo-controlled pivotal trial evaluating CRO for the prophylaxis of diarrhea in adults with solid tumors receiving 1 of 24 diarrheagenic TTx known to cause any grade diarrhea in ≥50% of patients. This study is designed to show a 40% reduction in loose/watery (LW) stools in patients randomized 1:1 CRO to placebo (1-sided α=0.025) and stratified by tumor type (lung, breast, other) and TTx type (CDK4/6i, TKIs, or other). Eligible patients require a new TTx, ECOG 0-2, lack baseline diarrhea and can complete patient-reported outcome (PRO) diary using a mobile device. Key exclusions include immunotherapy, neratinib or irinotecan (due to required SOC antimotility prophylaxis), colitis/ostomy/abdominal surgery ≤3 months, or antidiarrheal/laxative/antibiotic use ≤7 days. Oral CRO 125 mg or a matching placebo is administered twice daily concomitant with TTx initiation and continued for 12 weeks, with the option to continue blinded treatment through 24 weeks. Rescue antidiarrheal medication is permitted when participants have ≥4 LW stools and can continue thereafter. PRO diaries capture clinical and QoL outcomes. The primary endpoint is the mean weekly number of LW stools over 12 weeks based on PRO diary using the Bristol Stool Form Scale. Key secondary endpoints include time to TTx/ChemoRx dose reduction or discontinuation, time to ≥4 LW stools for 2 consecutive days, fecal incontinence episodes, and time to durable responder status (≤7 LW stools/week). PRO diaries capture: 1) LW stool frequency daily; 2) TTx/ChemoRx dose reduction/discontinuation, use of antimotility drugs, fecal incontinence daily; and 3) CTD’s impact on QoL weekly.

Results: Enrollment is complete with 287 patients from 46 sites in 5 countries from 8/2020 through 5/2023. Primary cancer diagnoses were breast (183; 64%), lung (37; 13%), renal (36; 12.5%), liver (12; 4%) and other (19; 6.5%). Most frequent TTx were CDK 4/6 and EGFR inhibitors. To our knowledge this trial evaluating CRO is the first prospective, randomized double blind study for prevention of targeted therapy CTD. Topline results for the study are expected in Q4 2023 and will be reported at the meeting.

Funded by Napo Pharmaceuticals (a Jaguar Health Co.)

Citation Format: Lee Schwartzberg, Pablo Okhuysen, Eric Roeland, Gregory Vidal, Kathleen Harnden, Richard Zuniga, Snezana Bosnjak, Sreedevi Daggubati, Daliborka Bursac. ONTARGET: Phase 3 randomized, double-blind, placebo-controlled trial evaluating crofelemer for the prophylaxis of diarrhea in adult patients with solid tumors receiving targeted therapies with or without standard chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-13-01.