BEIJING (REUTERS) - A pill containing two HIV drugs that was touted as a potential treatment for the novel coronavirus was not effective, according to a study released late on Wednesday in the New England Journal of Medicine.

A test in Chinese patients with severe Covid-19 disease found the 99 who received AbbVie Inc's Kaletra, a combination of lopinavir and ritonavir, fared no better than the 100 who received standard care.

People who received the combination showed small gains in the time to clinical improvement and mortality at 28 days, but the differences were not statistically significant.

People on the drugs showed clinical improvement after a median of 15 days compared to 16 days with standard care, a difference the researchers characterised as "significant, albeit modest".

The study results were published online in the New England Journal of Medicine.

The lopinavir-ritonavir combination also produced more side effects, prompting the treatments to be halted in 13.8 per cent of patients.

The drug combination was not tested against a placebo, which is the gold standard in assessing the effectiveness of a treatment.

All of the patients had pneumonia and were treated at Jin Yin-Tan Hospital in Wuhan, the city where the pandemic began.

The treatment "was not associated with clinical improvement or mortality in seriously ill patients with Covid-19 different from that associated with standard care alone", concluded the team, led by Dr Bin Cao of the National Clinical Research Centre for Respiratory Diseases.

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The test "was a heroic effort", Dr Lindsey Baden and Dr Eric Rubin, editors of the New England Journal of Medicine, said in a Journal editorial.

"Unfortunately, the trial results were disappointing."

The treatment "had no discernible effect" on the replication of the virus, which is how the therapy is supposed to work, they said.

The combination HIV therapy has been used by doctors in various countries in hopes of being effective. India's Union Health Ministry has been recommending the treatment.