PRA Health Sciences launched its initial public offering this morning, raising $306 million from the sale of nearly 17 million shares at $18 per share—below plans it announced in September to raise up to $375 million.

The stock price climbed 13% in early trading before settling to about $20 in the late afternoon.

Earlier this month Renaissance Capital reported PRA Health Sciences’ more bullish plans were to raise $400 million by offering 18.6 million shares at a price range of $20 to $23 per share.

Proceeds from the IPO—$286.5 million after underwriting, commission and offering expenses are deducted—will be used to reduce $258.6 million in debt, with the remaining net proceeds of nearly $28 million for general corporate purposes.

The fifth of the eight largest global CROs to go public, PRA Health Sciences’ launch comes less than a week after INC Research’s IPO raised $150 million, selling just over 8.1 million shares at $18.50. Since then, its shares have traded between $19.61 and $21.60 per share.

PRA Health Sciences’ IPO comes 16 months after PRA was acquired by private equity giant Kohlberg Kravis Roberts in a bidding war for $1.3 billion. Just a few months later, KKR acquired ReSearch Pharmaceutical Services and merged the two businesses. Late last year, KKR purchased CRI Lifetree to bolster PRA Health Sciences’ early-stage clinical trial capabilities.

KKR reportedly had planned to sell 1.6 million shares of its own stock alongside the IPO shares but chose not to proceed with that plan. After the IPO, KKR still will retain controlling interest in the business, which was founded in 1982.

With these acquisitions, KKR said PRA Health Sciences is now the fourth largest CRO. Of the top eight CROs—Quintiles, Covance, PRA Health Sciences, Parexel, PPD, Icon, INC Research and inVentiv—only two, PPD and inVentiv, still are held by private equity groups. Five are now publicly traded and one, Covance, was acquired by LabCorp earlier this month.

The CRO market has grown at an annual rate of 7%, in part because of the recent shift toward strategic partnerships with major sponsors, Ingo Bank, CFO of Parexel, told attendees this week at the Credit Suisse Annual Healthcare Conference in Phoenix.

“Clients are trusting us with an increasing number of products,” said Bank, “and some large biopharma companies are streamlining pipelines as necessary to be competitive, and this has led to increased outsourcing.”