Prosper Marketplace, long an also-ran of the financial startup world, is trying to make a comeback.

The San Francisco-based company on Wednesday said that it has raised $165 million in series D financing, from a group of investors led by big-name Wall Street banks. That round doubled its valuation to more than $1.9 billion, according to the Wall Street Journal.

Prosper was one of the first online loan marketplaces, or so-called "peer-to-peer" lenders. It was founded by Chris Larsen in 2006, beating now better-known competitor Lending Club into the business of disrupting banking. Both companies allow individuals and, increasingly, institutional investors to loan money directly to borrowers, as an alternative to traditional bank loans.

But Prosper struggled to adapt to financial regulations unveiled in 2008, and soon saw its business and its brand-name recognition outstripped by Lending Club. Larsen left in 2012, while Lending Club founder Renaud Laplanche steadily worked to expand his company. It went public in December, in a blockbuster IPO that initially valued the company at around $8 billion.

Still, being public hasn't been easy for Lending Club; its current market cap is $6.9 billion, and its stock is down 24 percent from its debut.

Now Prosper is trying to catch up. The company says it facilitated $1.6 billion in loan originations in 2014--more than four times its business in 2013.

That growth "demonstrates that a shift is in progress in the way that consumers borrow and lend," Chief Executive Aaron Vermut said in Prosper's funding release.

Prosper's investors were led by Credit Suisse NEXT Investors, part of the bank's asset management division; other investors included JPMorgan Chase's asset management division, SunTrust Banks, USAA, BBVA, Neuberger Berman Private Equity Funds, Passport Capital and Breyer Capital.