The drug development company, Pain Therapeutics, Inc., recently announced positive results from preliminary analysis of a large Phase II clinical trial with the drug PTI-555. PTI-555 is an investigational painkiller proposed as a substitute for morphine and similar narcotic painkillers.
This Phase II trial was a multi-center, randomized, double blind, placebo and active controlled human clinical trial comparing PTI-555 to morphine sulfate, and placebo.
The trial enrolled 210 patients with moderate to severe pain following major oral surgery significant enough to warrant opioid analgesia. Immediately after surgery, patients were randomly assigned to receive a single oral nominal dose of PTI-555, morphine sulfate, or placebo.
PTI-555 is a combination of morphine sulfate and low-dose naltrexone. The primary efficacy endpoint in this trial was pain relief within eight hours of dosing.
Patients given a single oral dose of PTI-555 90mg achieved significantly more total pain relief over four hours compared to patients given a single 90mg dose of oral morphine sulfate with no significant change in the incidence of side effects. In addition, patients given a single oral dose of PTI-555 90mg achieved significantly more total pain relief over four hours compared to patients given placebo.
Twenty-five percent of patients given a single oral dose of PTI-555 90mg achieved complete pain relief within eight hours of dosing, compared to just three percent of patients given a single 90mg dose of oral morphine sulfate.
PTI-555 was well tolerated and was not associated with any reported serious adverse events, either during the trial or the subsequent follow-up period. The percentage of patients reporting any drug related adverse events during the 24 hours following dosing was approximately the same in the two drug groups. Certain nervous system conditions, such as somnolence, fatigue, and euphoria, occurred less frequently in the PTI-555 treatment group.
“These positive results are an important clinical milestone for our initiative to develop a drug that’s better than morphine,” said Barry Sherman, M.D., executive vice president and chief medical officer of Pain Therapeutics, Inc. “The novel pharmacological theory that low doses of opioid antagonist can improve the performance of opioid agonists, such as morphine, continues to be supported in large numbers of patients.”