June 28 (Reuters) - Digital assets investment management firm 21Shares filed Friday for permission from U.S. regulators to launch an exchange-traded fund tied to the spot price of crypto token Solana.

It was the second such filing in as many days, following a similar move Thursday by VanEck. The Securities & Exchange Commission approved spot bitcoin ETFs offered by both firms, among others, in January after a long battle. Both VanEck and 21Shares are among the asset managers awaiting SEC approval to launch spot ETFs tied to the price of ethereum, the second-largest cryptocurrency.

The CBOE, the exchange on which both asset managers plan to list Solana ETFs if approved, must still request regulatory approval to change its rules and allow these new products to trade. People involved in the Solana discussions, who declined to be identified because of the confidentiality of the process, said that filing could come within days or weeks. A spokeswoman for CBOE declined to comment.

A third asset manager, Canada's 3iQ, filed earlier in June for permission from Ontario regulators to list a similar Solana-based product on the Toronto Stock Exchange. Solana is the fifth-largest cryptocurrency measured by market capitalization, according to CoinGecko.

The three filings have combined to drive the price of Solana 9.4% higher in the last seven days, even as the prices of bitcoin and ether dropped 4.6% and 2.8% respectively, according to CoinGecko.

So far, however, no futures contracts on Solana trade on the CME, in contrast to the pattern with both bitcoin and ether. The SEC approved futures-based ETFs tied to both tokens before considering the spot products.

The existence of futures contracts, however, "should not be the sole criterion for ETF eligibility," said Andrew Jacobson, head of legal at 21Shares. (Reporting by Suzanne McGee; Editing by Cynthia Osterman)