GlaxoSmithKline’s experimental diabetes medicine albiglutide lowered blood sugar better than Merck & Co.’s Januvia or Sanofi’s Amaryl, while more patients reported gastrointestinal side effects, in a study.

The experimental diabetes medicine albiglutide also didn’t work better than Takeda Pharmaceutial Co.’s Actos medicine, Bloomberg news reported.

However, overall, GSK (NYSE: GSK) said results from five studies indicate the drug’s efficacy.

“Albiglutide achieved the primary efficacy endpoint in these five studies, although a hierarchical analysis of noninferiority to pioglitazone was not met in one study, as noted [in a press release],” GSK said Monday.

“The most commonly reported adverse reactions in these studies were gastrointestinal (GI) complaints, primarily nausea and diarrhoea, and injection site reactions,” the company added.

Overall, the findings add to mixed results released so far by Glaxo, which has conducted eight late-stage studies on albiglutide. Glaxo has said the drug failed to help diabetics control their blood sugar as well as Novo Nordisk A/S’s Victoza in another trial.

“The data suggest that albiglutide is unlikely to be sufficient for it to be a serious competitor in the market,” said Sam Fazeli, a London-based analyst at Bloomberg Industries. “There is a small risk that the regulators would say that the the risk-benefit profile isn’t supportive of approval.”

About 10 percent of patients taking albiglutide reported nausea, compared with 7 percent of those taking Januvia and 6 percent on Amaryl, according to an summary of the 104-week study dubbed Harmony 3 that was presented at the American Diabetes Association’s annual meeting in Chicago. Vomiting and diarrhea were also more frequent among those taking albiglutide, the abstract said. All patients took the drugs with metformin.

Albiglutide’s once-weekly dosing would make the drug more convenient for patients compared with existing once-daily treatments. Still, it will face challenges as it enters a “crowded area,” Patrick Vallance, Glaxo’s head of pharmaceuticals research and development, said in an interview.

Glaxo submitted albiglutide to U.S. regulators in January and to European regulators in March. The company has said it’s seeking a partner to help market the drug.

It’s unlikely that sales of albiglutide will reach levels of Avandia, which was once the world’s best-selling diabetes pill with peak annual sales of of about $3 billion for Glaxo. That drug was withdrawn from the market in Europe in 2010 and sales were limited in the U.S. because of an increased risk of heart attacks.

Sales of albiglutide may reach $301 million in 2016, according to the average of nine analysts’ estimates compiled by Bloomberg.

GSK’s summary of the test results as disclosed Monday can be read online.

[GSK ARCHIVE: Check out more than a decade of GSK stories as reported in WRAL Tech Wire.]