Stocks were largely higher on Monday after overcoming a slow start to the trading week. By 2:30 p.m. EDT, the Nasdaq Composite (^IXIC 0.10%) had climbed about 0.2%, with aspirations to finish at an all-time high.

A couple of stocks contributed significantly to the positive mood on Wall Street. Tesla (TSLA 12.06%) is a perennial favorite among many investors, and its stock was among the best performers in the mega-cap arena. Meanwhile, tiny Celldex Therapeutics (CLDX -1.99%) enjoyed much larger gains that stemmed from good news about one of its candidate treatments. Below, we'll go into more detail about today's moves.

Person at desk with hands up in a celebratory gesture.

Image source: Getty Images.

Tesla gears up

Shares of Tesla were higher by 4%. The stock overcame negative comments from one set of Wall Street analysts even as CEO Elon Musk gave testimony about Tesla's purchase of its SolarCity unit from several years back.

One explanation for the optimism about the stock relates to Tesla's self-driving vehicle technology. The company started to enable vehicles whose owners paid in advance for incremental software updates to upgrade to the latest beta version of Tesla's autonomous driving software. Yet Tesla warned drivers not to assume too much about the driver assistance system, in an effort to avoid some of the accidents that have resulted from Tesla owners counting on their vehicles to do too much without any human intervention.

Yet analysts at Citi were skeptical about the release, arguing that early indications suggest minimal improvement in features. Citi is among the most bearish analysts on Tesla, with a sell rating and a price target of $175 per share.

Meanwhile, many shareholders are watching Musk's testimony in Delaware court, in which he's been asked to defend his role in Tesla's SolarCity acquisition. Naysayers have centered on family relationships between top-level executives at both companies. Cross-examination, however, got heated and seemingly personal.

Tesla's ability to move higher shows that shareholders are able to separate Musk's role from the future success of the company. That's a positive development and could support future gains for the electric car stock.

Celldex gets a win

Elsewhere, shares of Celldex Therapeutics moved higher by 23%. The little-known biotech got an early win with a key candidate treatment in its development pipeline.

Celldex released positive data late Friday on its CDX-0159 candidate treatment, which aims to help patients who are dealing with chronic urticaria, another name for hives. The phase 1b study involved 19 patients, and all but one of them had a complete response that included depletion of skin mast cells.

Obviously, it's still early in the clinical trial process, but CEO Anthony Marucci was still optimistic about the results. The Celldex leader believes that the news points to a higher probability that CDX-0159 could help patients with other related diseases as well, and he's hopeful that the treatment's indications will expand over time.

Celldex shares have quadrupled in price over the past year as investors have grown more optimistic about the company's monoclonal antibody biotechnology. If it can keep generating positive trial results, then Celldex could have a lot further to rise in the months and years ahead.