US-based AcelRx Pharmaceuticals has started dosing in the pivotal Phase III trial of ARX-04, a non-invasive, single-use 30mcg sufentanil sublingual tablet in a disposable, pre-filled, single-dose applicator (SDA), for the treatment of pain.

Scheduled to be conducted at four sites in the US, the multi-center, double-blind, placebo-controlled SAP301 trial will evaluate the efficacy and safety of ARX-04 vs. placebo to treat moderate-to-severe acute pain following ambulatory abdominal surgery.

A total of 160 adult patients will be included in the trial and they will be randomised 2:1 active to placebo, to be treated for about 48 hours.

During the trial, ARX-04 or placebo will be administered by site staff as requested by the patient, but it will not be more than once per hour.

The trial’s primary endpoint is to show a significant difference in the time-weighted summed pain intensity difference (SPID) of ARX-04 compared to placebo over a 12-hour dosing period (SPID-12).

AcelRx founder and chief medical officer Dr Pamela Palmer said: "We are pleased to have our pivotal ARX-04 Phase III clinical trial underway.

"The ARX-04 product represents a promising new application of our sublingual tablet technology for delivery of sufentanil and has the potential to safely provide non-invasive, fast-acting analgesia for patients in acute pain.

"We anticipate enrollment to take up to nine months. Pending the completion of enrollment in this study, we anticipate top-line results in the fourth quarter of 2015."

ARX-04 includes 30mcg sufentanil sublingual tablet, in a pre-filled SDA and the company’s tablet formulation enables sublingual sufentanil absorption when the drug is placed under the tongue.

As a result, ARX-04 can provide analgesia in a non-invasive method of administration and show a consistent pharmacokinetic profile due to a high percentage of drug being absorbed sublingually instead of through the gastrointestinal tract.