The stock market got off to a slow start on Monday, but it managed to finish the session with modest gains for most major benchmarks. Concerns about whether the U.S. and China will find a near-term solution to their trade disputes held indexes back from bigger moves higher, but the overall mood among investors stayed positive despite those worries. Some companies had extremely good news that sent their share prices up sharply. Peloton Interactive (NASDAQ:PTON), Yandex (NASDAQ:YNDX), and Karuna Therapeutics (NASDAQ:KRTX) were among the top performers. Here's why they did so well.

Peloton rides higher

Shares of Peloton Interactive rose 11%, extending their gains from last week and climbing above their September IPO price. Shareholders got a vote of confidence from billionaire investor George Soros last week, who reported in his quarterly filing with the U.S. Securities and Exchange Commission that he had added the interactive fitness equipment company's stock to his portfolio. Soros didn't take a huge position in Peloton, amounting to 1.575 million shares. Even at the new, higher price, with a value of less than $50 million, the holding won't make or break Soros' performance -- but it does show that the company has some support from a well-known investment icon.

Stationary bike with Peloton logo, along with display showing exercise program.

Image source: Peloton Interactive.

Yandex changes structure, starts buyback

Yandex saw its stock jump 12% after the Russian internet search specialist announced some changes to its corporate governance structure along with a $300 million stock repurchase program. Under the proposal, Yandex will give the right to name two members to its 12-member board of directors to a public interest foundation, which will also have the right to prevent any single entity from putting together more than a 10% interest in Yandex. A total of 11 directors will govern this foundation, drawing from five Russian universities and three non-governmental institutions, as well as from Yandex's management. The move addresses concerns from Russia's government about the company, and investors were pleased at the idea that there won't be a bigger battle between Yandex and the Kremlin.

The big Karuna

Finally, shares of Karuna Therapeutics more than quintupled, soaring 443%. The biopharmaceutical company released extremely strong results from a phase 2 study of its schizophrenia treatment KarXT, including meeting its primary endpoint of showing a significant average reduction on a scale measuring schizophrenia symptom severity. Moreover, Karuna didn't see signs of some common side effects from similar antipsychotic drugs, such as weight gain or drowsiness. Investors are excited about the prospects of Karuna going to the U.S. Food and Drug Administration next year to start a phase 3 study, as it could mean a game-changing breakthrough for sufferers of the disease.