Cathie Wood's Ark Invest and crypto investment firm 21Shares are seeking regulatory approval to set up an exchange-traded fund (ETF) that would directly hold ether, according to a filing with the U.S. Securities and Exchange Commission (SEC) on Wednesday.

It is the first attempt to list a fund in the U.S. that would directly invest in ether, the second-largest cryptocurrency by market capitalization.

In a boost to the crypto sector, the U.S. District of Columbia Court of Appeals last month passed a landmark ruling that the SEC was wrong to reject an application from crypto asset manager Grayscale Investments to list an ETF that tracks the price of bitcoin.

The case has been closely watched by the cryptocurrency and asset management industries, which have been trying for years to convince the SEC to approve a spot bitcoin ETF.

Cboe Global Markets earlier this year filed a proposal with the U.S. SEC to list and trade shares of a spot bitcoin ETF by Ark Invest and 21Shares on the Cboe BZX exchange. The SEC, however, delayed a decision on whether to approve it.

The regulator has in recent years rejected dozens of applications for spot bitcoin ETFs, citing inadequate levels of trading surveillance that could leave the underlying spot market subject to fraud and manipulation.

(Reporting by Jaiveer Singh Shekhawat in Bengaluru; Editing by Devika Syamnath)