Company Working Toward Once-Yearly Naltrexone Product

A life sciences company that has developed implant technology for sustained-release formulations of drugs has its sights set on a potentially groundbreaking improvement in adherence to medication treatment for opioid use disorder (OUD).

With Delpor, Inc., moving close to Phase 3 clinical trials for a sustained-release formulation of the antipsychotic risperidone for the treatment of schizophrenia, company leaders are now seeking to develop a once-yearly naltrexone product. Compliance with the oral version of naltrexone, one of three medications approved for OUD, has been poor, and the once-monthly injectable version sold as Vivitrol also has seen challenges in terms of follow-through after an initial injection.

Delpor president and CEO Tassos Nicolaou tells Addiction Professional that sustained release of therapeutic levels of the antagonist could prove to be a valuable tool in preventing relapse to opioid addiction. Animal studies of the naltrexone implant have indicated that the product is safe, and the company hopes to have a medication clinic-ready for the necessary human trials within one to two years.

“The good thing for us about naltrexone is that now we can leverage all the work we have done with risperidone,” says Nicolaou.

The company has received funding under the National Institutes of Health's (NIH's) Helping to End Addiction Long-Term (HEAL) initiative for the naltrexone implant development effort. It is expected to receive up to $5.7 million in an initial phase, with the possibility of continuation funding to complete development if initial efforts prove successful.

Development process

The device that Delpor works with is made of titanium and is around the size of a matchstick. It is implanted in the abdomen in a procedure that can be easily completed in a doctor's office with local anesthesia.

The technology is ideal as a delivery mechanism for drugs that have either a low dose or low bioavailability, Nicolaou says. In the case of naltrexone, the typical 50-mg dose is relatively high, but only a small percentage makes it into the patient's system, he says.

He says the company has screened around 30 central nervous system (CNS) drugs, and naltrexone has emerged as a top candidate. A key component of the feasibility research involves mixing the active drug with inactive “excipients” that serve as the medium for the drug's activity.

It took the company three to four years to answer the key questions needed for development of its first CNS implant, a 6-to-12 month product for delivery of risperidone, but Nicolaou believes the process should be much shorter for naltrexone now that the company can draw from the risperidone experience.

He says a naltrexone implant that would deliver the medication for up to a year could be useful for the treatment of both opioid and alcohol dependence, although the company's present focus is on opioids because of the current attention to the opioid crisis.

Nicolaou explains that another advantage of the implant technology lies in the fact that it is reversible in situations where a patient might have to receive opioids because of surgery, for example. The implant can be removed, after which plasma levels of naltrexone would drop within a day, he says.