Financial firms are once again lining up to attempt to get their proposed spot bitcoin exchange-traded-funds approved by the U.S. securities regulator after BlackRock this month unveiled it was looking to launch such a product.

Stock picker Cathy Wood's Ark Invest and Swiss-based exchange-traded fund (ETF) issuer 21Shares on Wednesday amended their bitcoin ETF application, while asset manager Fidelity is also expected to file a spot bitcoin ETF application, trade publication The Block reported on Tuesday.

The U.S. Securities and Exchange Commission (SEC) has rejected dozens of applications for spot bitcoin ETFs, saying the proposals have not met anti-fraud and investor protection standards.

These are the major firms with live SEC applications:

BLACKROCK - The world's biggest asset manager filed for a bitcoin ETF on June 15. BlackRock's iShares Bitcoin Trust, if approved, will trade on the Nasdaq and use Coinbase Custody as its crypto custodian and BNY Mellon as its cash custodian, according to a filing with the SEC.

BlackRock's filing hopes to clear remaining SEC hurdles through an arrangement with its planned listing market, Nasdaq, which said it would enter into a surveillance-sharing agreement with a bitcoin spot trading exchange to supplement its own surveillance program.

ARK AND 21SHARES US - Ark Invest and 21Shares on April 25 filed for a third time to launch the ARK 21Shares Bitcoin ETF, which would trade on Cboe's BZX exchange under the ticker ARKB and use Coinbase Custody Trust Company as its custodian.

The SEC on Jan. 26, 2023, and March 31, 2022, rejected previous filings by Cboe BZX to list the ETF, saying the exchange did not meet the burden that its rules be "designed to prevent fraudulent and manipulative acts and practices" and "to protect investors and the public interest."

On June 28, 2023, Cboe BZX amended its rule filing with the SEC to include a surveillance-sharing agreement with a bitcoin spot trading exchange to supplement its own surveillance program.

WISDOMTREE - WisdomTree filed on June 20 for approval to launch the WisdomTree Bitcoin Trust on the Cboe BZX exchange under the symbol BTCW, using U.S. Bank, National Association as its custodian.

The SEC on Oct. 11, 2022, and Dec. 1, 2021, rejected previous Cboe BZX rule filings to list a WisdomTree spot bitcoin trust, stating the exchange did not meet its legal burden to ensure its rules be "designed to prevent fraudulent and manipulative acts and practices" and "to protect investors and the public interest."

INVESCO AND GALAXY DIGITAL - Invesco reactivated its September 2021 application to launch the Invesco Galaxy Bitcoin ETF on Cboe's BZX exchange.

VANECK - VanEck refiled on June 22 to for approval to launch the VanEck Bitcoin Trust on Cboe's BZX exchange.

The SEC on March 10, 2023, and on Nov. 12, 2021, rejected rule filings by the Cboe BZX exchange to list and trade shares of a VanEck bitcoin trust, saying the exchange did not meet the burden that its rules be "designed to prevent fraudulent and manipulative acts and practices" and "to protect investors and the public interest."

VALKYRIE DIGITAL ASSETS - Valkyrie filed with the SEC on June 21 to launch the Valkyrie Bitcoin Fund on the Nasdaq under the ticker BRRR.

The SEC on Dec. 26, 2021, rejected a previous filing by NYSE Arca to list a spot bitcoin ETF by Valkyrie, saying the exchange did not meet the burden that its rules be "designed to prevent fraudulent and manipulative acts and practices" and "to protect investors and the public interest."

(Reporting by John McCrank; Editing by Michelle Price and Daniel Wallis)