* Austin cites co's deteriorating performance
* Shares up 43 pct
July 6 (Reuters) - Chelsea Therapeutics International Ltd's largest shareholder has urged the board to explore alternative approaches after the company's key experimental drug hit another regulatory road block, sending its shares up 43 percent.
Josiah Austin, who owns 12.39 percent of Chelsea's stock, said he was alerting the company in light of its deteriorating performance, a regulatory filing showed.
"I would welcome the opportunity to sit down with management and the board to discuss steps that can and should be taken now to enhance shareholder value, including an infusion of fresh perspective on the Board," Austin wrote to CEO Simon Pedder.
Chelsea said on Tuesday that U.S. regulators recommended an additional trial for its rejected hypotension drug Northera, further delaying the launch of the treatment.
Nothera is the most advanced clinical candidate of Chelsea, which does not have any approved products.
The Charlotte, North Carolina-based company's shares, which plunged to an eight-year low on Tuesday, rose to $1.30 on Friday on the Nasdaq.