Biotech Warrants and Convertible Notes: Hidden Dilution

The problem: You bought a small biotech, the stock ran 40% on good data, and then a follow-on offering with warrants put you underwater without the share count you watch ever changing. You read the headline “shares outstanding” number and missed the fact that warrants and convertible notes were dilution that had not hit the share count yet.

The solution: Read the fully diluted share count, not the headline count. Fully diluted means shares outstanding plus everything that can turn into shares: in-the-money warrants, options, and convertible notes. The three instruments below are where biotech hides that future dilution.

Step 1: Know the three instruments

A warrant is the right to buy a share at a fixed strike price before an expiry date. It is not a share yet. It becomes one when the holder pays the strike. So a warrant at a $2 strike only turns into a share if the stock stays above $2, and the company collects the $2, not the market price.

A pre-funded warrant is the same thing with a strike of about one-tenth of a cent ($0.0001). The holder pays almost the full share price up front, then exercises the warrant for a penny later. Why? Because a holder who owns more than 4.99% or 9.99% of a company trips disclosure and control thresholds it does not want to trigger. The pre-funded warrant lets an investor effectively buy the shares now while staying under the cap on paper.

A convertible note is debt that converts into equity. The company borrows cash now, and the lender gets the right to convert the note into shares later, usually at a discount or premium to the stock price at the time. It is “non-dilutive” until the stock runs and the note converts. Then the dilution appears.

Step 2: Why biotech leans on them

Pre-revenue biotechs have one way to raise money: sell new shares. Warrants are the sweetener that gets a discounted offering done.

SPACs are the cleanest example. When a biotech goes public via SPAC, the SPAC’s original warrants survive the merger and trade alongside the stock. The reverse-merger playbook explains the structure, but the key is that the warrant overhang is built in from day one.

Follow-on offerings are where warrants do the most damage. INOVIO priced a $20 million public offering on July 29, 2026 that sold 21.1 million shares plus warrants to buy up to 42.1 million more at a $1.10 strike, twice the share count in warrant coverage, and the stock fell about 21% when the deal priced. Outlook Therapeutics ran the same play on August 12: $55 million raised by selling 55.6 million shares plus warrants for another 55.6 million at $1.10, a combined price of $0.99 per share plus warrant. The warrants roughly doubled the eventual share count.

Step 3: Do the dilution math

The number that matters is fully diluted shares outstanding: shares outstanding, plus in-the-money warrants, plus options, plus the shares the convertible notes will turn into. The standard way companies report it is the treasury stock method, which assumes every in-the-money warrant or option is exercised and counts the new shares, less any shares the company could buy back with the proceeds.

The worked example: a company has 50 million shares outstanding and 30 million in-the-money warrants. Fully diluted, that is 80 million shares, a 60% overhang. Every buyout price and every per-share valuation gets re-priced against the 80 million, not the 50 million. A $100 million acquisition looks like $2.00 a share on the headline count and $1.25 a share on the fully diluted count. That gap is where retail holders get wiped out.

Step 4: Where to find the real number

Three places, in order. The 10-Q has a potentially dilutive securities note and, for companies using the treasury stock method, the reconciliation table that shows the jump from basic to diluted shares. The offering prospectus, the S-1 or 424B, has the exact warrant terms: strike, expiry, and coverage ratio. And the SEC EDGAR full-text search will surface every warrant and convertible note the company has ever issued. The SEC filings guide walks the 10-Q and 10-K reading order.

The easiest check is the one in the dilution survival guide: watch whether shares outstanding grows faster than the dilution you already priced in. Warrants exercising over quarters show up as a creeping share count, the same way an ATM facility does.

Step 5: Read the red flag

Heavy warrant coverage is a signal the company raised from weakness, not strength. A biotech attaching warrants for as many or more shares than it is selling is telling you the underwriters could not get the deal done at a clean price. That usually means the runway is short, under 6 to 12 months, and the company had to take whatever terms the market would give.

The same signal shows up in the 8-point M&A screen as the forced-seller pattern: a company that keeps raising with warrant sweeteners is one that keeps getting squeezed, and a forced seller is exactly the kind of name an activist or a buyer targets. The accounting red flags guide covers the balance-sheet version of the same weakness.

Common mistakes

• Reading the headline share count and skipping the fully diluted number. The overhang is the real denominator.
• Treating a convertible note as free money. It converts when the stock runs, which is exactly when you thought you were winning.
• Ignoring warrant coverage on an offering. INOVIO sold 21.1 million shares with warrants for 42.1 million more. The market saw the second number; most retail holders saw the first.
• Assuming pre-funded warrants are exotic. They are just a way for an investor to stay under a 4.99% or 9.99% ownership cap while still buying the shares.

Final checklist

• Pull the fully diluted share count from the 10-Q, not the headline number
• Check the warrant terms in the S-1 or 424B: strike, expiry, coverage
• Convert every convertible note into its eventual share count at the conversion price
• Re-run any buyout or valuation math against fully diluted shares
• Flag any offering with warrant coverage at or above 1:1 as a weakness signal

Warrants and convertible notes are not inherently bad. They are the cost of being a pre-revenue company that has to raise before it can earn. Your job is to see the future shares before they hit the count, because the market will price them in whether you do or not.