Stocks making the biggest moves in the premarket: Twitter, Sirius XM, Nektar Therapeutics and more

cnbc.com:

Take a look at some of the biggest movers in the premarket:

Twitter (TWTR) – Twitter shares jumped 4.5% in the premarket after the company's board of directors adopted a so-called poison pill to prevent Tesla (TLSA) CEO Elon Musk from increasing his stake in the company past 15%. That follows Musk's $54.20 per share bid for Twitter last week.

Sirius XM (SIRI) – The satellite radio operator's stock fell 2% in premarket trading after Morgan Stanley downgraded it to «underweight» from «equal-weight.» Morgan Stanley said auto market headwinds would negatively impact Sirius XM, and also noted the stock's outperformance over the past year.

Nektar Therapeutics (NKTR) – The drugmaker's shares cratered 24.4% in the premarket after it halted all trials involving its key cancer drug. The experimental treatment did not produce the desired results in multiple studies.

Bank of America (BAC) – Bank of America reported quarterly profit of 80 cents per share, 5 cents a share above estimates. Revenue also topped Street forecasts on strength in consumer lending. Bank of America shares rose 1.1% in the premarket.

Bank of New York Mellon (BK) – The bank beat estimates by a penny a share, with quarterly earnings of 86 cents per share. Revenue was essentially in line with analysts' predictions. Its results were helped in part by higher interest rates.

Synchrony Financial (SYF) – The financial services company reported quarterly profit of $1.77 per share, beating the consensus estimate of $1.54 a share. Revenue came in above estimates as well.  Synchrony's board also approved the addition of $2.8 billion to the company's stock buyback plan as well as a 5% dividend increase to 23 cents per share.  Synchrony added 1% in the premarket.

Southwest