Vocus Inc, a maker of cloud-based software for marketing and public relations, said it would be bought by private equity firm GTCR Valor Merger Sub Inc for about $447 million.
GTCR will offer $18 per Vocus share, a premium of 48 percent to the stock's close on Friday.
Vocus shares rose 47 percent to $17.92 on Monday morning, making the stock the top percentage gainer on the Nasdaq.
The company recently shifted its focus to mid-sized companies from small businesses, but is struggling to sell its software to its new target clients, who want more sophisticated products, Robert W. Baird & Co analyst Steve Ashley said.
Beltsville, Maryland-based Vocus has not posted a full-year profit since 2008.
The company owns online press release service PRWeb, social media marketing company North Social, email marketing company iContact and Help a Reporter Out service for journalists.
Reuters reported last month that Vocus was looking to sell itself and had attracted interest from companies such as Web.com Group Inc.
Ashley said in an email on Monday that the valuation for Vocus seemed fair and he did not expect other bidders for the company.
"We think it makes sense (for Vocus) to sort out its operational and strategic issues as a private company, rather than playing it out in the public realm," Barrington Research Associates analyst Jeff Houston said.
GTCR will also buy Vocus's Series A convertible preferred stock for $77.3 million.
Stifel was Vocus's financial adviser for the deal, which is expected to close in the second quarter of 2014. The deal includes a termination fee of $13 million.
(Editing by Don Sebastian and Kirti Pandey)