Merck & Co. Inc. said a phase 3 study showed that its Delstrigo drug was as effective as current therapy in suppressing HIV-1 levels in patients who switched to the company's medicine, meeting the main goal of the trial.

The study evaluated Delstrigo — a once-daily fixed-dose combination tablet of doravirine 100 milligrams, lamivudine 3TC 300 mg and tenofovir disoproxil fumarate 300 mg — in adults with HIV-1 infection who demonstrated virological suppression, or undetectable viral load, for at least six months on a stable antiretroviral treatment regimen.

Participants in the clinical trial, known as Drive-Shift, either switched to Delstrigo at the start or after continuing on their current treatment for 24 weeks. Of those who switched immediately, 90.8% of them had plasma HIV-1 RNA viral load levels of less than 50 copies per milliliter at 48 weeks into the study, compared to 94.6% of those who remained on their baseline therapy and had similar viral load levels at week 24.

A secondary comparison showed that 93.7% of patients who immediately switched to Delstrigo had suppressed viral load at week 24, compared with 94.6% of those who continued on their baseline therapy at the same timepoint.

Kenilworth, N.J.-based Merck found no genotypic or phenotypic resistance to any study drug in participants taking Delstrigo through 48 weeks of treatment.

At week 24, study participants who switched to Delstrigo on day 1 showed statistically significant decreases in fasting LDL-cholesterol and non-HDL-cholesterol compared to those who continued on a boosted protease inhibitor regimen. Delstrigo also showed decreases in cholesterol and triglyceride levels. Patients on HIV treatment have been known to develop high cholesterol, and drugmakers are focusing on reducing such long-term effects while maintaining viral suppression over time.

The most common untoward medical occurrences were common cold and headache. The most common drug-related side effect was headache. The rates of discontinuation of therapy due to side effects through week 24 were 2.5% in those who immediately switched to Delstrigo and 0.4% in the baseline regimen group.

The results are scheduled to be presented on Oct. 4 at the IDWeek 2018 conference in San Francisco.

"Data from this trial support another possible future option for people living with HIV, many of whom may require a change to a different treatment regimen," said Princy Kumar, chief of the division of infectious diseases and tropical medicine at MedStar Georgetown University Hospital and a professor at the Georgetown University School of Medicine in Washington.

In August, the U.S. Food and Drug Administration approved Delstrigo, along with Merck's other HIV-1 drug Pifeltro, for treating the infection in adults who have not previously received antiretroviral treatment. In September, the European Medicines Agency recommended the approval of both medicines for the same indication.