Regulators in the USA have confirmed that they are not going to approve NiCox’ investigational pain drug naproxcinod, news that has hammered its share price.

The French drugmaker says it has received a complete response letter from the US Food and Drug Administration related to the New Drug Application) for naproxcinod, which has been developed for the relief of the signs and symptoms of osteoarthritis. The agency says that its review of the NDA is complete and that it does not approve the application.

The rejection comes as no surprise given that in May, the FDA’s Arthritis Drugs and Drug Safety and Risk Management Advisory Committees voted 16 to one (with one abstention) that they did not have sufficient evidence to support the approval of naproxcinod. The panel noted that the treatment, an improved version of naproxen, a non-steroidal anti-inflammatory drug that can increase blood pressure and cause stomach problems, appeared to be more effective than placebo but was not necessarily shown to be as effective as naproxen, which is available generically.

In the CRL, the agency recommends conducting “one or more” long-term controlled studies to assess the cardiovascular and gastrointestinal safety of naproxcinod, the first in a new class of drugs known as CINODs (COX-inhibiting nitric oxide-donators). Additional studies to demonstrate “a clinically meaningful therapeutic benefit attributable to the nitric oxide donation were also recommended”, though NiCox noted that no clinical efficacy trials were requested.

The Sophia Antipolis-based company, which notes that naproxcinod is still under review in Europe, said it plans to discuss the CRL and potential next steps as early as possible with the FDA. NiCox goes on to say that it remains well funded and had cash and equivalents of 138.5 million euros at the end of March.

The company added that it has no long-term debt and is “constantly reviewing all aspects of its cost base to ensure careful conservation of its funds”. However this morning its market capitalisation has taken a thumping and NiCox shares were down 24% at 2.16 euros at 9.45am (UK time).