Sept 14  - US stocks ended sharply higher on Monday as signs of progress in developing a COVID-19 vaccine and a spurt of multibillion-dollar deals lifted investor optimism.

Drugmaker AstraZeneca resumed its British clinical trials of its COVID-19 vaccine, one of the most advanced in development.

Also, Pfizer Inc rose after the drugmaker and German biotech firm BioNTech SE proposed to expand their Phase 3 pivotal COVID-19 vaccine trial to about 44,000 participants.

"The market loves anything with a vaccine because that is the ultimate solution here. And we'll see more and more headlines," on that going forward, said Tim Ghriskey, chief investment strategist at Inverness Counsel in New York, New York. Merger-related news also lifted the market, he said. Nvidia Corp jumped on plans to buy UK-based chip designer Arm from Japan's SoftBank Group Corp for as much as $40 billion, in a deal set to reshape the global semiconductor landscape. The Philadelphia SE chip index also rose.

Oracle gained as the cloud services company said it would team up with China's ByteDance to keep TikTok operating in the United States, beating Microsoft Corp in a deal structured as a partnership rather than an outright sale.

US stocks are coming off of two straight weeks of losses as investors sold heavyweight technology shares that had powered the benchmark index to record highs in a dramatic recovery from its March lows.

Unofficially, the Dow Jones Industrial Average rose 321.54 points, or 1.16%, to 27,987.18, the S&P 500 gained 42.29 points, or 1.27%, to 3,383.26 and the Nasdaq Composite added 203.11 points, or 1.87%, to 11,056.65.

All of the S&P 500 sectors were higher, and tech heavyweight Apple Inc gave the S&P 500 its biggest boost.

Tesla Inc's shares rebounded after losses last week.

Later this week, investors will focus on the Federal Reserve's last policy meeting before the Nov. 3 US presidential elections.

In other deal news, Immunomedics Inc's shares jumped after Gilead Sciences Inc's $21 billion buyout deal, which is a steep premium to the biotech company's closing price on Friday.

Reuters