Merck launches expanded access programme for integrase inhibitor

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Merck has announced that its experimental integrase inhibitor MK-0518 will be made available through a worldwide expanded access programme for people with HIV who have run out of other drugs and who are at risk of clinical illness or immunologic deterioration. Merck says that the programme will begin within the next few months subject to regulatory review and approval in individual countries.

MK-0518 showed promising results in a phase II dose-ranging study presented earlier this year. Up to 72% of highly treatment-experienced patients who received MK-0518 in combination with a background regimen optimised by resistance testing achieved a viral load below 50 copies/ml within 16 weeks, compared to just 8% in the placebo arm.

People with HIV will be eligible to receive MK-0518 if they meet the following criteria:


resistance testing

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


Term used to indicate how well a particular drug is tolerated when taken by people at the usual dosage. Good tolerability means that drug side-effects do not cause people to stop using the drug.

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.

optimised background therapy

When a new drug is added to a failing HIV regimen, the other drugs in the regimen (the 'background therapy') may also be changed. Any changes are based on a person’s resistance test results and treatment history. Optimised background therapy gives a new HIV regimen (or an experimental HIV drug being studied in a clinical trial) the best chance of succeeding. 

integrase inhibitors (INI, INSTI)

A class of antiretroviral drugs. Integrase strand transfer inhibitors (INSTIs) block integrase, which is an HIV enzyme that the virus uses to insert its genetic material into a cell that it has infected. Blocking integrase prevents HIV from replicating.

  • documented HIV-1 infection
  • at least 16 years old
  • limited treatment options or no treatment options available to them due to resistance or intolerance to multiple anti-retroviral regimens,
  • are not achieving adequate virologic suppression on current regimen and be at risk of clinical or immunologic progression
  • clinically stable

Patients are excluded from the study if they have received MK-0518 in a clinical trial, require any medications prohibited by the protocol, have acute hepatitis due to any cause or clinically significant chronic liver disease, have a condition which the investigator deems will interfere with adherence and safety, or are pregnant.

Patients will receive open-label MK-0518 400 mg twice daily, in addition to optimised background therapy (OBT). Investigators will select the OBT based on the patient’s prior treatment history and antiretroviral resistance testing. OBT will not be provided by Merck. Safety and tolerability of MK-0518 will be monitored and the expanded access programme will collect safety data on all patients.

The programme will make MK-0518 available to participants until three months after the drug has been licensed in the local market.