Phase 3 Trial for Sublingual Sufentanil for the Treatment of Moderate-to-Severe Acute Pain

ARX-04 would provide a non-invasive option for moderate-to-severe acute pain in medical settings.

Phase 3 trials are underway for ARX-04, a sufentanil tablet (30 µg) by Acel Rx Pharmaceuticals. This pharmaceutical company based in Redwood City, CA specializes in the development of therapies for the treatment of moderate-to-severe acute pain.

Sufentanil is a synthetic opioid analgesic with very high potency (500 times that of morphine); it is mostly administered intravenously for short-term pain relief during surgery and/or critical care, but is also used for off-label purposes intrathecally. Because of its high potency and high affinity for opioid receptors, sufentanil is indicated for opioid-dependent individuals, as well as for patients on a buprenorphine regimen for chronic pain. Animal studies showed rapid uptake of sufentanil through mucosal tissues.1

Acel Rx Pharmaceuticals announced on June 28, 2016 completion of patient enrollment in ARX-04 phase 3 trials. Two open-label studies remain in this phase: SAP302 and SAP303. In SAP302, 76 adult patients having presented in the ER with trauma- or injury-related moderate-to-severe acute pain were included in the study. Summed pain intensity difference (SPID) was assessed at one hour and compared to baseline. Patients in the SAP303 study had undergone surgery requiring general or spinal anesthesia (n=40, age >40); in those, SPID at 12 hours was used as primary endpoint for sufentanil efficacy.

The company anticipate results from these studies to be released in the third quarter of 2016. The chief medical officer and co-founder of AcelRx said in statement: “Pending positive results for SAP302 and SAP303, we believe we are on track to file a New Drug Application for ARX-04 with the U.S. Food and Drug Administration (FDA) by the end of this year.”

ARX-04 would provide a non-invasive option for moderate-to-severe acute pain in medical settings, ranging from inpatient surgery with short hospital stay to the emergency room.


1. Mather LE. Opioids: a pharmacologist’s delight!. Clin Exp Pharmacol Physiol. 1995;22(11):833-6.