US-based biopharmaceutical firm Cara Therapeutics has started dosing first subjects in a Phase Ia/Ib clinical trial of an oral tablet formulation of its peripherally-selective kappa opioid agonist, CR845, for treatment of acute and chronic pain.

The double-blind, randomised, placebo-controlled trial will assess the pharmacokinetic and safety profile of single and multiple escalating doses of oral CR845.

In addition, the trial will evaluate activation of kappa opioid receptors through the measurement of an established neuroendocrine biomarker used in a previous Phase I trial of a capsule formulation of oral CR845.

Around 150 healthy volunteers will be enrolled in the trial at a single US site and will evaluate up to six concentrations of the tablet formulation of oral CR845.

"Oral CR845 has the potential to address the significant unmet medical need for a safer, non-abusable alternative to narcotic opioids and NSAIDs for the treatment of moderate-to-severe acute and chronic pain."

Top-line pharmacokinetic, safety and biomarker data from the trial is expected to be announced in the fourth quarter of 2014.

Cara Therapeutics president and chief executive officer Derek Chalmers said: "Oral CR845 has the potential to address the significant unmet medical need for a safer, non-abusable alternative to narcotic opioids and NSAIDs for the treatment of moderate-to-severe acute and chronic pain."

CR845 is a peripherally acting kappa opioid receptor agonist being developed for treatment of acute and chronic pain.

In multiple randomised, double-blind, placebo-controlled Phase II trials in patients undergoing laparoscopic hysterectomy or bunionectomy procedures, treatment with IV CR845 resulted in significant reductions in pain intensity and opioid-related side effects.

In more than 400 subjects dosed so far, IV CR845 was found to be safe and well-tolerated, without incurring the dysphoric and psychotomimetic side-effects that have been reported with centrally acting (CNS-active) kappa opioid receptor agonists.

The oral tablet formulation of CR845 was synthesized using the peptide formulation technology developed by Enteris Biopharma under a Manufacturing and Clinical Supply Agreement.

The company is focused on developing and commercialising new chemical entities designed to alleviate pain by selectively targeting kappa opioid receptors.