Tuesday was a solid day on Wall Street, with major market benchmarks pushing upward into positive territory after having started the session on a sluggish note. With weakness in overseas markets during the long holiday weekend, investors worried that the negative sentiment would extend into U.S. trading as well. But generally upbeat earnings reports from some key companies helped to improve the mood, and other good news lifted individual stocks higher. Intercept Pharmaceuticals (NASDAQ:ICPT), PG&E (NYSE:PCG), and Superior Energy Services (NYSE:SPN) were among the top performers. Here's why they did so well.

Intercept gets good news on liver-disease drug

Shares of Intercept Pharmaceuticals picked up 6% after the biotech company announced the latest results of a key clinical trial. Intercept's phase 3 study of obeticholic acid in patients with liver fibrosis due to nonalcoholic steatohepatitis (NASH) successfully met a primary endpoint of fibrosis improvement without worsening of NASH. Intercept said that the drug also managed to resolve the liver disease with no worsening of fibrosis, but that primary endpoint didn't reach a statistically significant level. Nevertheless, the study only required one of the two endpoints be met, and the company now intends to file for approval of obeticholic acid in the U.S. and Europe during the second half of the year. That could both help liver patients and boost Intercept's business prospects.

Multiple sets of power lines hanging between two towers, near sunset.

Image source: Getty Images.

PG&E gets an upgrade

Utility giant PG&E saw its shares rise almost 15% following positive comments from stock analysts. Analysts at Citigroup upgraded the stock from neutral to buy, an unusual move given the fact that PG&E is still under bankruptcy protection. Nevertheless, Citi believes that the California utility is likely to get help from state lawmakers, who are looking at measures to reduce the ultimate liability that utility companies generally bear for wildfires sparked by power lines. If that happens quickly, it could provide a path toward a full recovery for PG&E, and investors are betting on that favorable bailout coming sooner rather than later.

Superior Energy responds to changing industry conditions

Finally, shares of Superior Energy Services soared 23%. The oil-field services company continued to face tough conditions, but its adjusted net losses for the fourth quarter of 2018 were far narrower than what it suffered in the year-earlier period. Revenue bounced higher by nearly 9% from the fourth quarter of 2017, and CEO David Dunlap pointed to the company's strategy that "large-scale, mature shale development programs are an excellent opportunity for Superior Energy in the years to come." Despite some needs to control capital spending in the short run, more favorable moves in energy markets lately suggest that Superior's building momentum from past quarters and moving in the right direction.

Check out the latest Superior Energy, PG&E, and Intercept Pharmaceuticals earnings call transcripts.