A health ministry panel is questioning Novartis Pharma K.K.'s use of clinical research data in promoting the sale of Diovan, its drug to lower blood pressure, saying it "could constitute misleading advertisement" after revelations that some of the data were manipulated.

The Japanese unit of Swiss pharmaceutical giant Novartis AG promoted its product, released in Japan in 2000, by claiming it works better than competitors' rival drugs in reducing strokes and angina, according to the panel's interim report.

While the panel expressed concern that the scandal may have tainted the credibility of clinical research conducted at Japanese institutions, there appear to still be many hurdles in getting to the bottom of the case.