UBS, a major player in the blank-check boom captivating Wall Street, has quietly banned its financial advisers from pitching SPAC stocks to wealth management clients, CNN Business has learned. The restrictions, which haven’t been previously reported, highlight the elevated risk of playing in what is one of the hottest corners of finance right now. Special purpose acquisition companies (SPACs) are shell companies that exist only to take private firms public through reverse mergers. Although these kinds of deals were once frowned upon, SPACs have become all the rage, with major companies including Virgin Galactic, DraftKings and Playboy all going public this way. SPACs have raised more than $80 billion so far in 2021, up 2,000% from this point last year, according to Dealogic. The recent involvement of pro athletes, singers and politicians is raising concern among US financial regulators. Earlier this month, UBS\n \n (UBS) decided its wealth management clients in the Americas will be allowed to trade SPAC shares only on an unsolicited basis, a person familiar with the matter told CNN Business. In other words, UBS advisers are not permitted to call their wealthy clients to encourage them to buy or sell specific SPACs trading on the open market. Once the newly merged entity has gone public, the UBS advisers will be allowed to pitch the stocks. A UBS spokesperson declined to comment. The decision was made, the person familiar with the matter said, because of the limited availability of information and research on SPACs before they merge with private companies. Some SPACs ‘make no sense’ Indeed, little is known about SPACs until they determine what company they will target to bring public. SPACs don’t have operating businesses, just a blank check and a management team hunting for the right merger candidate. The SPAC restrictions at UBS do not extend to SPAC IPO offerings. UBS financial advisers are still able to review these so-called primary SPAC offerings with eligible clients in deals where UBS is an underwriter of the IPO, the person said. (Private banks like UBS typically only offer these deals up to wealthy clients with net worth above a specified level.) The SPAC restrictions by UBS come as some experts, including former Federal Reserve officials and famed investor Jeremy Grantham, worry the blank-check boom is overdone. US-listed SPACs have already raised more money this year than in all of 2020 — and the year’s first quarter hasn’t even ended. “If you look at the SPAC market, there’s some really attractive new companies and new technologies coming to the market that are financing effectively,” Rick Rieder, BlackRock’s chief investment officer of global fixed income, told CNN Business this week. “And then there are some that make no sense.” Rieder expressed concern about how some SPACs will ever be able to grow into the elevated multiples they are garnering. “You’ve got to be really selective about where you go and not just jump onto that train because it’s gotten crazy,” he said. Big banks like UBS are cashing in Celebrities including Alex Rodriguez, Jay-Z and Ciara Wilson have all lent their star power to SPACs in recent months. The SEC issued a warning last week urging investors not to buy SPACs simply because of a celebrity’s involvement. “Celebrities, like anyone else, can be lured into participating in a risky investment or may be better able to sustain the risk of loss,” the SEC said. Big banks, including UBS, are cashing in on the SPAC craze. Investment banks receive fees in exchange for finding buyers for SPAC shares and putting a floor beneath their share price. These fees are not as large as what Wall Street firms make on traditional IPOs, but the sheer volume of SPAC deals have helped make up for that. UBS was the primary underwriter, or book runner, on 22 US-listed SPACs last year, sixth among major Wall Street firms, according to Dealogic. The Swiss bank was one of the lead underwriters, along with Citigroup, for Bill Ackman’s SPAC, which raised $4 billion last July and is still hunting for a merger candidate. UBS has led another 15 SPACs so far this year, according to Dealogic. UBS is actively hiring in this booming part of the capital markets business. A week ago, the company listed a position on LinkedIn for a New York-based investment banker squarely focused on SPACs. Martin Blessing, the former co-president of UBS Global Wealth Management, reportedly launched a SPAC earlier this week aimed at buying a financial technology company. It’s not clear whether other major banks are imposing similar restrictions. Wells Fargo declined to comment, while representatives from firms including Goldman Sachs, Bank of America and JPMorgan did not respond to inquiries.