UPDATE 1-Swiss pharma firm Relief, U.S. partner fight after hopes dented for COVID-19 drug

(Adds detail about updated trial results, share performance)

ZURICH, April 19 (Reuters) - A Swiss company whose market capitalization rose at one time to more than 1.5 billion Swiss francs ($1.6 billion) on hopes an old drug it owned would succeed against COVID-19 is embroiled in a dispute with U.S. partner NeuroRx, it said in a statement.

Relief Therapeutics’ market cap has fallen about 70% from a high in the third quarter of 2020, as the company’s aviptadil, a 50-year-old medicine, failed to win U.S. emergency approval and in February demonstrated no survival benefit at 28 days in a U.S. clinical trial of people with COVID-19 respiratory failure.

The two companies said in March that 60-day results showed the drug helped patients, after adjusting for how they were ventilated and where they were treated, and announced plans to again pursue U.S. emergency approval.

Relief said on Monday that NeuroRx and it are fighting over issues including sharing of trial data, invoices totaling about $4 million that NeuroRx contends Relief must pay, funding for clinical trials, the allocation of potential profits, and other issues.

“Relief intends to continue its efforts to resolve amicably the pending disputes with NeuroRx over the Collaboration Agreement,” Relief said in a statement. “However, if such disputes are not resolved amicably, Relief intends to take all necessary actions to enforce its rights under the Collaboration Agreement.”

The shares, which are volatile, fell 18.2% by 1320 GMT.

Separately, a Securities and Exchange Commission filing on Friday by a special acquisition corporation that in December announced a merger with NeuroRx contends Relief had “reimbursed NeuroRx for approximately $10.6 million of expenses, but has not paid approximately $4 million in invoiced costs associated” with the aviptadil clinical trial.

“These circumstances may lead to a dispute with Relief Therapeutics regarding what share of profits Relief Therapeutics should be entitled to receive,” according to the SEC filing by Big Rock Partners Acquisition Corp.

$1 = 0.9206 Swiss francs Editing by Simon Cameron-Moore and Michael Shields