U.S. stock indexes drifted mostly higher in afternoon trading Friday, paring back earlier losses but still on track to end lower for the week. The Nasdaq composite index was weighed down by a slide in semiconductor stocks. The Dow Jones industrial average gained 45 points, or 0.3 percent, to 16,704 as of 1:10 p.m. Eastern time. The Standard & Poor's 500 index was down less than one point to 1,928. The Nasdaq composite lost 36 points, or 0.8 percent, to 4,341.

The FDA approves Gilead Sciences, Inc. (NASDAQ:GILD) Harvoni for the treatment of chronic hepatitis C genotype 1 infection. Harvoni is a combination of ledipasvir and sofosbuvir. It is the first approved regimen that does not require administration with interferon or ribavirin. This is the third HCV drug approved in the last 12 months. The agency cleared Janssen's (JNJ +0.3%) Oysio (simeprevir) in November 2013 and Sovaldi in December 2013.

The Texas Attorney General files a lawsuit in state court accusing AstraZeneca plc (ADR) (NYSE:AZN) of illegally marketing its antipsychotic Seroquel (quetiapine fumarate) for unapproved uses and paying kickbacks to physicians and state health officials. The Texas AG's action builds on whistleblower suits that have been filed by two former AZN sales reps.

Aastrom Biosciences (NASDAQ:ASTM) plans to change its name to Vericel Corporation and move its corporate base from Michigan to Cambridge, MA. The name change is contingent on shareholder approval.

Exact Sciences (NASDAQ:EXAS) is up 35% on increased volume. Yesterday after the close the company announced the establishment of Medicare coverage for Cologuard. The specific coverage is testing once every three years in asymptomatic patients of age 50 - 85 years who are at average risk of developing colorectal cancer.

 Ebola-related issues continue to head north. Alpha Pro Tech (NYSEMKT: APT) is up 29%  on strong volume. Lakeland Industries (NASDAQ:LAKE) is up 7% on moderate volume.