Background: ORIN1001 is a first-in-class small molecule with a novel, unique enzyme and mode of inhibition that selectively inhibits Inositol Requiring Enzyme 1α (IRE1) RNAse and blocks X-Box Binding Protein 1 (XBP1) activation in the endoplasmic reticulum (ER). IRE1α/XBP1 has been implicated in a host of pathologies, and molecules that modulate it are under intense investigation for the treatment of oncologic, metabolic, neurodegenerative and other diseases. ORIN1001 has demonstrated preclinical anti-tumor activity alone and in combination with standard of care across multiple animal models including breast, prostate, lung, liver, pancreatic, brain, colon, ovarian, esophageal, and hematologic cancers and is now undergoing first-in-human testing. Methods: A phase 1, open label, 3+3 dose escalation trial is testing ORIN1001 administered PO daily to patients (pts) with advanced solid tumors (single agent) or relapsed refractory breast cancer (in combination with Abraxane). The phase 1 dose escalation part of the trial evaluates the safety, tolerability, pharmacokinetics and preliminary efficacy of ORIN1001. After identification of the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) for the single agent, the dose expansion part of the trial will test ORIN1001 in combination with Abraxane. Results: As of Jan 25, 2021, 22 patients with advanced cancer have received ORIN1001 dosed at 100mg, 200mg or 300mg per day in 21-day continuous cycles with a median age of 61 (range 42-77). The pts had received a median of 4 prior line of treatments. Two DLTs were observed at 200 mg with thrombocytopenia and rash. MTD has not been reached. Common (>15%) treatment-emergent adverse events (TEAEs) included nausea, vomiting, rash, fatigue, and hypokalaemia. The vast majority of these events were Grade 1-2 in severity. Seven (32%) pts had at least 1 TRAE grade≥ 3, the most frequent of which were thrombocytopenia (N=3) and rash (N=3). Preliminary pharmacokinetic analysis showed ORIN1001 exposure to increase in a dose proportional manner. Mean t_1/2 at steady state was 18 hrs. Thirteen pts were evaluated for preliminary efficacy. Best response, per RECIST 1.1, was stable disease (SD) in 8 pts while 5 pts had progressive disease (PD). For 2 ongoing patients with advanced liver or colorectal cancer, duration of treatment has exceeded 300 days and 570 days, respectively. Conclusions: To date, the phase 1 part of the first-in-human trial has demonstrated a reasonable safety and pharmacokinetic profile for ORIN1001 at 100mg and 200mg dose levels. While efficacy data have yet to mature, chronic dosing achieved in pts with heavily treated advanced solid tumors, suggests clinical potential for in the setting of advanced solid cancers. The phase 2 part of the trial testing ORIN1001 in combination with Abraxane is currently enrolling pts with advanced breast cancer. Clinical trial information: NCT03950570