What Is an FDA AdCom? Panel Vote Moves Biotech Stocks

You own a biotech stock with a PDUFA date six weeks out. The stock has been running. Then the FDA schedules an advisory committee meeting two weeks before the PDUFA. You don’t know what that means, so you hold. The panel votes 6-3 against approval. The stock drops 35% before you can react. The PDUFA date becomes a formality.

An FDA advisory committee (AdCom) is a panel of outside experts who vote on whether to recommend approval. The vote is non-binding, but the FDA follows it the large majority of the time. A negative vote roughly doubles the probability of a CRL.

What an AdCom actually is

The FDA doesn’t have enough internal expertise to evaluate every controversial drug application. So it convenes advisory committees: panels of external physicians, statisticians, pharmacologists, and patient representatives who review the application, ask questions of the sponsor and FDA staff, and vote on whether to recommend approval.

The vote is advisory. The FDA makes the final call at the PDUFA date. But the FDA follows the AdCom vote roughly 85% of the time overall, and concurs with negative votes even more often. A 2023 study published in JAMA Internal Medicine found the FDA agreed with 97% of “yes” votes. The “no” votes are where the real risk lives. The FDA follows those the majority of the time, and a negative AdCom vote roughly doubles the probability of a CRL.

The full calendar of upcoming meetings is on the FDA advisory committee calendar. The main committees biotech investors track: ODAC (Oncologic Drugs), CTGTAC (Cellular, Tissue, and Gene Therapies), PDAC (Psychopharmacologic Drugs), and AMDAC (Anti-Infective Drugs).

Step 1: Find out if an AdCom is scheduled

Not every drug gets an AdCom. The FDA convenes them for controversial or novel applications. When one is scheduled, it typically falls 4 to 8 weeks before the PDUFA date.

Three sources, in order of usefulness:

1. The FDA advisory committee calendar. The definitive source. Meetings are posted weeks to months ahead.
2. BioPharmCatalyst.com. Aggregates AdCom dates alongside PDUFA dates in one view.
3. The company’s press release. Companies must disclose when the FDA schedules an AdCom for their application. Search “[ticker] advisory committee” or check the investor relations page.

Example: Moderna announced its mRNA-1010 flu vaccine AdCom for June 18, 2026, ahead of the August 5 PDUFA. Anyone reading that release had the date marked seven weeks out.

Step 2: Understand why the FDA called one (or didn’t)

The FDA calls an AdCom when it wants outside input. The usual triggers:

• Controversial efficacy. The effect size is marginal, or the primary endpoint barely met.
• Novel mechanism of action. First-in-class drugs where the FDA has no internal precedent.
• Safety signal. Unexpected serious adverse events or deaths that require expert interpretation.
• Surrogate endpoint concerns. Especially in accelerated approval, where the surrogate’s link to clinical benefit is unproven.
• Trial design questions. The control arm, endpoint choice, or patient population is debatable.

When the FDA skips the AdCom, it’s a positive signal. It means the agency is comfortable with the data and doesn’t see controversial issues worth a panel discussion. BridgeBio received word that the FDA was “not currently planning” an AdCom for encaleret in ADH1. Read our BridgeBio encaleret write-up for how that de-risking signal played out. The FDA saw nothing controversial enough to convene a panel.

Step 3: Watch the vote

AdCom votes are public. The meeting is webcast on FDA.gov, and the vote typically happens on the same day. The vote question is usually phrased as some variant of: “Do the benefits of [drug] outweigh the risks for the treatment of [indication]?”

Two outcomes:

• Positive vote (yes). The stock typically jumps 10 to 30% on the vote day. The PDUFA becomes a high-probability approval event. Moderna’s mRNA-1010 AdCom voted 9-0 in favor on June 18, 2026. The stock moved on the de-risked approval path into the August PDUFA.
• Negative vote (no). The stock typically drops 20 to 40% on the vote day. The PDUFA becomes a formality. A CRL is highly likely. If you own the stock and the AdCom votes no, that is your exit signal. Do not wait for the PDUFA.

Step 4: Position before the AdCom, not on the vote

The edge in AdCom trading is the same as PDUFA trading: the move happens in the positioning before the event, not in the reaction to it. Traders who buy 2 to 4 weeks before the AdCom and exit on the vote capture the move. Traders who wait for the vote headline buy the pop (on yes) or eat the drop (on no).

Size for binary risk. A single pre-AdCom position should not exceed 2 to 5% of a portfolio, the same rule as pre-PDUFA trades. If you cannot stomach a 40% loss on the position, the position is too big. Our guide to investing in biotech stocks covers position sizing for binary catalysts.

Step 5: Know when the AdCom replaces the PDUFA as the catalyst

For some drugs, the AdCom is the real catalyst and the PDUFA is a formality. This is especially true when:

• The AdCom vote is negative (CRL is likely at PDUFA).
• The AdCom vote is strongly positive (9-0 or 8-1, approval is likely at PDUFA).

In both cases, most of the move has already happened by the PDUFA date. Capricor’s deramiocel DMD AdCom on July 29, 2026 is a current example. The AdCom is the event that will shape the PDUFA outcome, not the other way around. Read our Capricor deramiocel AdCom write-up for the setup. Similarly, Replimune’s RP1 melanoma AdCom in late July 2026 is the binary event ahead of the August 2 PDUFA. See our Replimune RP1 write-up.

Common mistakes

• Holding through a negative AdCom vote. The panel vote is the signal. The PDUFA date is the formalization. If you wait for the CRL to sell, you sell 40% lower than the post-AdCom price. Our CRL guide covers this in detail.
• Ignoring the AdCom entirely. Some investors only track the PDUFA date and don’t know an AdCom is scheduled. The AdCom can move the stock more than the PDUFA.
• Treating a positive AdCom vote as guaranteed approval. The FDA follows the vote roughly 85% of the time, not 100%. A positive vote de-risks the PDUFA but doesn’t guarantee it.
• Buying the stock the day before the AdCom. You’re paying the run-up premium to bet on a binary vote. The edge is earlier, not at the door. Our PDUFA guide covers why the edge is in the run-up.
• Not checking which committee is reviewing. A gene therapy reviewed by CTGTAC (the gene therapy committee) is different from an oncology drug reviewed by ODAC. The committee’s expertise and track record matters.

Final checklist

• AdCom date confirmed from FDA calendar or company press release
• Vote question understood (benefit-risk, or specific endpoint)
• Position sized to 2 to 5% of portfolio
• Exit plan for positive vote (hold into PDUFA) and negative vote (sell on the vote) written down
• Not buying the day before the AdCom
• If no AdCom is scheduled, check whether the FDA skipping it is a positive signal (clean data) or a negative one (the FDA doesn’t need input because the data is clearly insufficient)