Gilead's stock price at last check fell 1% to $78.86 after an analyst at UBS cut his rating to neutral from buy.
The move marks the third analyst downgrade for Gilead in little more than a week, coming on the heels of cuts by analysts at Wells Fargo and BMO Capital, according to Bloomberg.
Even so, UBS analyst Navin Jacob raised his price target $3 to $80 a share.
UBS's Jacob emphasized that the cut was not based on any shift in the investment firm's belief in the potential success of Gilead's experimental anti-viral drug remdesivir, which it still pegs at greater than 50%, the news service reported.
Rather, the cut is based on the current value of Gilead's shares, the UBS analyst wrote, citing a greater risk/reward balance after the stock price ran up sharply since the beginning of February.
Shares of Gilead were trading at $64.03 on Jan. 30, with the biopharma company seeing a series of spikes over the past two and a half months amid news of its efforts to develop a Covid-19 treatment. The shares rose even as the overall market tanked.
Reports on how effective remdesivir has been in treating patients struggling with covid-19 have so far been inconclusive.
The World Health Organization last week pulled down the results of a study of the drug in China that gave a bullish spin on the results.
Gilead said the report on the WHO website included "inappropriate characterizations of the study.'