Biotech Reverse Mergers and SPACs: Backdoor IPO Playbook

You saw “Company X to go public via reverse merger” and bought the stock. Three months later it’s down 40%, and you can’t figure out why the company “raised $150 million” but the stock kept falling. The problem: a reverse merger is not an IPO, and the number in the headline is rarely the number in the bank.

The solution: before you buy any reverse merger or SPAC biotech, answer three questions. How much cash does the company actually have after the deal closes? Who owns what after dilution? And when does the lock-up expire?

Step 1: Learn what a reverse merger actually is

A reverse merger is a private company merging into an existing public company, usually a failed biotech that still has a stock listing and some cash. The private company’s shareholders end up owning most of the combined entity, and the old public company’s shareholders get diluted down to a sliver. The private company gets the listing without running a traditional IPO roadshow.

Three of these closed in a single week in August 2026. Skye Bioscience reverse-merged with Redx Pharma to form Fibrx, keeping Skye’s Nasdaq listing. Werewolf handed its listing to Ambros for the CRPS drug neridronate. These are survival deals, not premium buyouts.

Step 2: Know the two structures, because they dilute differently

A reverse merger uses an existing operating company as the shell. A SPAC (special purpose acquisition company) is a blank-check company that raised cash in its own IPO specifically to find a private company to merge with. Both get a private company public, but the mechanics differ.

In a SPAC, the sponsor puts up roughly $25,000 for founder shares that become a 20% promote in the merged company. That 20% comes out of everyone else’s pocket. The SPAC’s IPO cash sits in a trust account, and shareholders can redeem for roughly $10 per share instead of staying in. High redemptions mean less cash actually reaches the biotech. PIPE financing (private investment in public equity) then fills the redemption hole, and PIPE investors get shares, often at a discount.

The Oak Hill Bio SPAC shows the pattern: roughly $175 million in gross proceeds, $75 million from the trust backstopped by sponsor RA Capital plus $100 million in committed PIPE, to take the Angelman syndrome drug rugonersen public.

Step 3: Do the dilution math, because that’s where the money goes

The headline number is not the cash. A reverse merger that looks like a $200 million deal may carry $50 million in PIPE, $30 million in sponsor promote, and $20 million in fees. The private company nets $100 million, not $200 million.

Read the ownership split in the deal press release. In the Skye/Redx deal, pre-transaction Skye holders kept 5.38%, Redx investors got 46.17%, and the new financing syndicate took 48.45%. In the Werewolf/Ambros deal, Ambros holders got 71.7%, legacy Werewolf holders kept 6.8%, and the $150 million PIPE took 21.5%. Legacy shareholders in both cases were diluted to single digits. Skye holders also got a contingent value right to 90% of any future proceeds from monetizing nimacimab, the paused anti-obesity program. A CVR is a promise, not cash, and it often pays zero.

Step 4: Check the cash and the runway, not the valuation

Once you know who owns what, check how much cash the company actually has and how long it lasts. The Oak Hill Bio raise funds a Phase 3 start, but the company will likely need more capital to finish the trial. A reverse merger that funds the company through its next readout is one thing. A listing that just delays the next dilutive raise by two quarters is another. The definitive numbers live in the 8-K and the proxy statement filed with the SEC, not the press release, and that is where you find the PIPE discount and the fee load. Pull the post-close cash balance from the SEC EDGAR filings, not from the headline.

Step 5: Find the lock-up expiration and mark it on your calendar

Insiders and PIPE investors are usually locked up for 180 days after the deal closes. When the lock-up expires, they can sell, and for reverse mergers this is often the top. Forced selling into a small float is brutal. Mark the date and treat it as a sell signal unless there’s a hard catalyst before it. This is the same mechanic as a traditional IPO lock-up, covered in the lock-up expiration guide.

Step 6: Ask the three questions before you buy

One: how much cash does the company actually have post-close, and how many quarters does it fund? Two: who owns what after dilution, and what did the old shareholders get reduced to? Three: when does the lock-up expire, and is there a catalyst before it? If you can’t answer all three from the filings, you’re gambling on a structure you don’t understand. For the full framework on vetting any biotech listing, start with the IPO evaluation guide.

Common mistakes

Buying the headline instead of the ownership split. The Werewolf/Ambros deal valued the combined company at roughly $500 million, but legacy Werewolf holders kept 6.8%. If you owned HOWL, you watched your stake shrink to almost nothing even if the merged company succeeds.

Ignoring redemption risk. SPAC shareholders can redeem for about $10 a share instead of staying in. High redemptions leave the biotech with far less cash than the deal announced, which forces another raise sooner.

Treating a reverse merger like an IPO. IPOs raise fresh primary capital into the company. Reverse mergers mostly recapitalize the private company’s existing shareholders, and the cash that shows up is often PIPE money, not the headline number.

Buying into a lock-up. If insiders can sell in 90 days and there’s no readout before then, you’re providing exit liquidity.

Final checklist

• Structure identified (reverse merger vs SPAC)
• Ownership split read (what % do legacy holders keep)
• Post-close cash and runway pulled from the S-4 or proxy on SEC EDGAR
• PIPE size and discount noted
• Lock-up expiration date marked
• Catalyst on the calendar before the lock-up expires
• Position sized for a 30-40% lock-up drawdown