The Nasdaq Composite and S&P 500 were up in late-morning trading Monday, while the Dow Jones Industrial Average was roughly flat after US lawmakers took a step toward reopening the federal government.

In company news, over 1,400 flights were canceled as of 7:15 a.m. ET on Monday, and that number is expected to grow, Bloomberg reported, citing data compiled by aviation analytics firm Cirium. Shares of United Airlines (UAL) and Delta Airlines (DAL) were down 0.9% and 0.3%, respectively. Shares of American Airlines (AAL) and Southwest Airlines (LUV) were down 1.6% and up 1.2%, respectively.

Metsera (MTSR) said late Friday it signed an amended merger agreement with Pfizer (PFE) under which Pfizer will acquire Metsera for up to $86.25 per share. The new consideration consists of $65.60 per share in cash and a contingent value right entitling holders to additional payments of up to $20.65 per share in cash. Metsera said its board determined that the revised terms represent the "best transaction" for its shareholders and that the deal proposed by Novo Nordisk (NVO) presents "unacceptably high legal and regulatory risks." Metsera shares were down past 15%, while those of Pfizer and Novo Nordisk were down 1.8% and up 0.1%, respectively.

Papa John's International (PZZA) is closing in on a deal worth $65 per share to be taken private, ABC Money reported. Papa John's shares were up more than 15%.

TreeHouse Foods (THS) has signed a deal to be acquired by Industrial F&B Investments III for $22.50 per share in cash, or about $2.9 billion, the companies said Monday. Separately, TreeHouse Foods reported Q3 adjusted earnings Monday of $0.43 per diluted share, down from $0.74 a year earlier and below the FactSet consensus analyst estimate of $0.56. Third-quarter net sales were $840.3 million, up from $839.1 million a year ago but below the FactSet consensus of $850.5 million. TreeHouse shares were up past 23%.

iHeartMedia (IHRT) and TikTok said Monday they have formed a partnership that includes the launch of the TikTok Podcast Network that will include 25 new podcasts hosted by TikTok creators. iHeartMedia shares were down 5.1%.

Price: 96.48, Change: -0.96, Percent Change: -0.98