The New Jersey-based drugmaker said it will not file a worldwide marketing application for MK-0524B in 2007 following formulation problems with the tablets, which combine Zocor with MK-524A, itself a combination drug composed of extended-release niacin and a selective flushing pathway inhibitor, DP-1 selective antagonist.
No new filing date has been set and the nature of the formulation problem was not disclosed, despite media reports suggesting there is an issue with the controlled release of the active ingredients.
Cholesterol-lowering drugs are the largest-selling category of drugs in the world but their market, currently valued at $32bn (€25bn) globally, is becoming more generic, as successful drugs such as Merck's Zocor and Bristol Myers Squibb's Pravachol (pravastine sodium) come off patent, so drugmakers are turning to combined formulations that are more popular with patients because they are cheaper than paying for two prescriptions and are often more effective.
Merck is vying for dominance of the lucrative cholesterol market after Zocor, which was the second-leading prescription drug behind Pfizer's Lipitor (atorvastatin calcium) in the US last year with $4.4bn in sales, became susceptible to generic competition in June.
But alarm bells went off at Merck last February when it informed researchers that it was encountering formulation problems with MK-524B, so clinical trials had to commence with administering MK-524A separately from Zocor.
Merck's latest disappointment however is welcomed news for Kos Pharmaceuticals, which is racing to seek US approval in the first half of 2007 for its own cholesterol combination product.
Kos's drug Simcor couples the active ingredient in generic Zocor with Niaspan, its widely used long-acting form of niacin.
There are also other players in this co-formulation arena; in July Abbott asked Irish biotechnology firm Elan to use its NanoCrystal technology to develop an "all in one" oral dose formulation combining two cholesterol drugs, AstraZeneca's Crestor (rosuvastatin) and Abbott's Tricor (fenofibrate), as demand for combination therapy, now 15 per cent of the cholesterol market, continues to grow.
Nevertheless, Merck does not appear phased with this latest setback and is continuing enrollment for a 20,000-patient international study known as HPS2-THRIVE (Treatment of HDL to Reduce the Incidence of Vascular Events), which will investigate the benefit of the co-administration of MK-0524A and Zocor on cardiovascular disease.
Even if combination pills are a long way from overtaking statin drugs, which generated $16bn in US sales last year according to IMS Health, the fact that the drug's industry's most lucrative sector sees such an interest in combined formulation speaks volumes about the potential of this developmental approach.