In the 10-day monotherapy trial, patients taking MK-0518 achieved a 98% reduction in HIV-RNA across all dosages tested, and at least half achieved HIV-RNA copies of 400 per ml or less.
The drug could be the first in a new class of investigational anti-retroviral therapy (ART) called integrase inhibitors that may inhibit the integrase enzyme from inserting HIV viral DNA into the human gene. Inhibiting integrase from performing this essential function blocks the ability of the virus to replicate and infect new cells.
“This study further demonstrated proof-of-concept for the antiviral activity of HIV integrase inhibitors as a new and exciting class of anti-retroviral agents,” said Dr Robin Isaacs, executive director, Infectious Disease and HIV Vaccine Clinical Research, MSD. “MK-0518 was generally well tolerated and demonstrated potent short-term viral load reduction as monotherapy in this small, early trial.”
In the trial MK-0518 therapy was generally well tolerated. The most common adverse experiences were headache, fatigue and dizziness; these were similar between the MK-0518 and the placebo groups.
It is estimated that up to 78% of patients treated with anti-retroviral drugs have developed resistance to more than one therapeutic class of these medicines. The problem of resistance also has increased substantially in drug-naive patients. The proportion of treatment-naive patients who carried resistant virus has grown to more than 20% today from 8% in 1999.