* CSL first half NPAT $1.2 bln, in line with analysts
* Company upgrades FY guidance to top of $1.88-1.95 bln range
* Shares down 4 pct (Recasts with investor reaction, adds shares, investor comment)
By Byron Kaye
SYDNEY, Feb 13 (Reuters) - Australian biotech giant CSL Ltd CSL.AX on Wednesday posted a 10 percent jump in first-half profit, meeting forecasts, but investors sold the shares heavily amid concerns its blockbuster growth was slowing and it may face regulatory delays in China.
The harsh reaction to an as-expected result reflects investors' high hopes for a company which has seen its shares surge by a third in a year, making it the country's fifth-biggest, following a 2015 acquisition in the U.S. vaccine market.
The former government laboratory said U.S. vaccine sales helped lift net profit to $1.2 billion in the December half, in line with most analyst forecasts, and upped its full-year guidance to be around the top of the previously provided range of $1.88 billion to $1.95 billion.
The company also declared an interim dividend of 85 cents per share, up from 79 cents last year.
But sales of some blood plasma products fell. The company also experienced weaker sales of a blood circulation product in China after buying its own supply licence there, a move it said gave it more control over distribution but still required regulatory approval.
"We do expect them to come through," said Chief Executive Paul Perreault on an analyst call. "The timing of the approval of the CFDA is not up to me, the regulators do not always adhere to my timelines," he added, referring to the China Food and Drug Administration.
CSL shares were down 4 percent by mid-session on Wednesday, their biggest intraday fall since October, while the broader market .AXJO was flat.
"There was some weakness in China but it looks like temporary weakness," said Sean Sequeira, chief investment officer at Alleron Investment Management.
"This result bodes well for their future, it shows they are executing according to their plan (but) the reaction so far is possibly because (investors) wanted a little bit more."
CSL's vaccine unit, Seqirus, which generates a fifth of overall sales, saw pre-tax profit rise 61 percent, while the company's larger blood plasma products division saw pre-tax profit shrink 2 percent.
In a statement, Perreault said demand for CSL's plasma products continued to be strong and its plan to open 30 to 35 new collection centres during the current financial year was on track.