Image source: Getty Images.

Stocks slipped from their morning highs in the afternoon but still logged solid gains on Monday. The Dow Jones Industrial Average (DJINDICES:^DJI) and the S&P 500 (SNPINDEX:^GSPC) indexes both added nearly 0.5%.

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Data source: Yahoo! Finance.

Volatility in commodity prices produced large swings in a few popular exchange-traded funds. The United States Oil Fund ETF rose 3% as crude oil passed $50 per barrel. The heavily leveraged gold fund, Direxion Daily Gold Miners Bull ETF, magnified a small increase in the price of its base commodity to tick up by 1%.

As for individual stocks, Twitter (NYSE:TWTR) and Tesaro (NASDAQ: TSRO) were two of the market's biggest movers on Monday. 

Twitter buyout chatter dies out

Twitter shares lost 12% as investors reacted to its shrinking hopes for a buyout. The social media specialist's stock soared last week on news that several companies, including Salesforce, were looking into acquiring its popular news platform. Yet after investors in these companies revolted, a premium-priced merger now looks like a long shot. In fact, none of the potential bidders is likely to make an offer, according to a report by Bloomberg over the weekend. 

It makes sense that Twitter shares have fallen to below where they were before the acquisition rumors started, since several of its most likely purchasers apparently chose to pass rather than make a bid for its assets. So, now the focus can now turn to its operating results, which aren't expected to be especially strong.

Twitter is projecting a sharp slowdown in sales growth when it posts third-quarter earnings results on Oct. 27. As usual, usage metrics and monetization numbers will be important to watch in that release. CEO Jack Dorsey will also likely go into detail about how the company plans to win in the area of live video, which Facebook and Twitter agree is a critical social media growth area.

Tesaro succeeds with its ovarian cancer drug

Tesaro jumped 19% after the biotech company released encouraging test results for its key drug, the ovarian cancer treating pill niraparib. A phase 3 trial showed that the drug succeeded in lengthening remission times between chemotherapy treatments in both groups of patients that it targeted.

Image source: Getty Images.

For BRCA mutation carriers, niraparib produced an average of 21 months of progression-free survival versus less than 6 months for a placebo pill. For non-BRCR mutation types, the result was 9 months compared to 4 months for the placebo. "We believe the results of this Phase 3 study demonstrated a meaningful benefit for women with platinum sensitive, recurrent ovarian cancer," Chief Operating Officer Mary Lynne Hedley said in a press release. Niraparib "could lengthen the interval between rounds of platinum-based chemotherapy," which would be "very meaningful for patients with ovarian cancer, who often live with a fear of recurrence after ending active treatment," said the trial's principle investigator.

Tesaro is looking into prospects for getting niraparib into the market through four ongoing trials, and this latest round of results only bolsters the case for the drug to quickly begin finding commercial success. The FDA has granted it fast-track status, and Tesaro believes it can complete its submission for full approval before the end of 2016.

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