Myriad halts HIV maturation inhibitor drug programme

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Myriad Pharmaceuticals is to halt its research programme designed to develop an HIV maturation inhibitor, the company announced on June 7th.

Maturation is the last stage in the production of HIV before it buds from a human cell, and an effective and safe maturation inhibitor would offer another new class of drug for patients with extensive drug resistance.

Myriad had the only remaining research programme in this area, having bought bevirimat, the maturation inhibitor developed by struggling biotechnology pioneer Panacos. Myriad was engaged in pre-clinical research into another promising maturation inhibitor, MPI-461359.



In vitro research or research involving animals, undertaken prior to research in humans.

drug resistance

A drug-resistant HIV strain is one which is less susceptible to the effects of one or more anti-HIV drugs because of an accumulation of HIV mutations in its genotype. Resistance can be the result of a poor adherence to treatment or of transmission of an already resistant virus.


The physical form in which a drug is manufactured or administered. Examples of formulations include tablets, capsules, powders, and oral and injectable solutions. A drug may be available in multiple formulations.

phase II

The second stage in the clinical evaluation of a new drug or intervention, in which preliminary data on effectiveness and additional information about safety is collected among a few hundred people with the disease or condition.

resistance testing

Laboratory testing to determine if an individual’s HIV strain is resistant to anti-HIV drugs. 

Bevirimat was being tested in a phase IIb study which began in December 2009. The drug was being tested in patients resistant to three antiretroviral drug classes, and compared to a two- or three-drug regimen optimised by resistance testing.

The company did not reveal whether adverse results from that study had been the cause of its decision to halt the maturation inhibitor programme, but said in a press statement that it will now seek to partner with another company to develop its maturation inhibitors further.

This week’s decision indicates the difficulties now faced by small drug companies as they attempt to develop new agents at a time of venture capital famine. The development of bevirimat had been dogged with formulation difficulties, and and an analysis of an earlier study indicated that the drug would be ineffective for a significant minority of patients due to naturally occurring resistance present before the drug was taken.