Gilead Sciences (GILD) posted an unexpected drop in Q1 revenue amid a surprising miss from cancer drug Trodelvy, Oppenheimer said Thursday in a report.

The biopharmaceutical company said Thursday that Q1 revenue fell to $6.67 billion from $6.69 billion a year earlier, trailing the $6.81 billion expected by analysts surveyed by FactSet. Trodelvy sales fell 5% to $293 million from a year earlier.

HIV product sales were expected to decline from the previous quarter, while the 17% drop on Trodelvy "was more surprising," Oppenheimer said.

Gilead's management said approval of AstraZeneca's (AZN) rival cancer drug Datroway hasn't had any impact, and "the simplest explanation is that Q4 was an outlier" with Trodelvy sales seen accelerating, the report said.

Excluding antiviral medication Veklury, Gilead "still delivered decent top-line growth" and returned $1.7 billion to shareholders in dividends and share buybacks, the report said.

Oppenheimer cut the price target on Gilead's stock to $125 from $132 and reiterated its outperform rating.

Gilead shares fell 2.8% in recent Friday trading.

Price: 103.22, Change: -2.93, Percent Change: -2.76