How to Invest in Biotech: PDUFA Dates, Trials, Catalysts

You’ve seen the headlines. A biotech stock jumps 80% in a day on FDA approval. So you find the next biotech with an upcoming FDA decision, buy shares, and wait. The FDA sends a Complete Response Letter instead. The stock drops 60% by market open.

That’s biotech investing. I’ve done it, and I’ve lost money doing it the wrong way. Here’s what I wish someone told me.

The problem

Biotech investing is fundamentally different from investing in tech or consumer stocks. Apple has revenue, earnings, and a product people buy every day. A pre-approval biotech has none of that. It has a drug in trials, a burn rate, and a date on the FDA calendar. The stock moves on binary outcomes: the drug works or it doesn’t. The FDA approves or it doesn’t. There is no “modest growth” in biotech catalysts.

The solution

Learn the framework: understand clinical trial phases, track FDA catalysts using free tools, pick a strategy that matches your risk tolerance, and never put more than 2-5% of your portfolio in a single pre-approval biotech play.

Step 1: Understand the four clinical trial phases

Before you invest in any biotech, know where the company’s drug is in the development pipeline. Here are the four phases:

Phase 1 tests safety in 20-100 healthy volunteers or patients for cancer drugs. The goal: find the maximum tolerated dose and check that the drug doesn’t kill people. About 70% of drugs pass Phase 1. This tells you almost nothing about whether the drug works, only that it’s safe enough to keep testing.

Phase 2 tests efficacy in 100-300 patients who have the disease. This is the first look at whether the drug actually does something. Roughly 33% of drugs that enter Phase 2 eventually make it to Phase 3. Phase 2 data can move a stock 30-50% in a day, but it’s not enough for FDA approval.

Phase 3 is the registrational trial: 300-3,000 patients, randomized, double-blinded, comparing the drug to a placebo or standard of care. This is the data the FDA uses to decide on approval. Phase 3 success is the single biggest stock-moving catalyst in biotech. Phase 3 failure can cut a stock in half overnight.

If you want to read Phase 2 or Phase 3 data critically rather than just trusting the headline, check our guide on how to read a clinical trial press release without getting fooled.

Step 2: Learn what a catalyst is (and track them)

A catalyst is any event that can move a biotech stock based on science or regulatory news, not earnings. The four main types:

1. PDUFA date: The FDA’s deadline for responding to a drug application. The agency has 10 months for a standard review and 6 months for a priority review. On or before the PDUFA date, the FDA issues a decision: approval, a Complete Response Letter, or occasionally a delay. This is the most common biotech catalyst. For a deeper dive on what these dates mean and how the FDA sets them, see our guide to PDUFA dates.

2. Clinical trial readout: Top-line results from a Phase 2 or 3 trial. If the trial met its primary endpoint, the stock usually jumps. If it missed, the stock crater. Moderna (MRNA) had its mRNA-1010 flu vaccine go before an FDA advisory committee on June 18, 2026, with a unanimous 9-0 vote in favor. The PDUFA date is August 5, 2026.

3. Advisory Committee (AdCom): A panel of outside experts votes on whether to recommend approval. The FDA usually follows the panel’s recommendation but not always. AdCom votes are scheduled and public, so you can plan around them.

4. sNDA/sBLA filing: A supplemental application to expand an approved drug’s label to a new indication. Merck (MRK) has an sBLA under review for ENHERTU in HER2+ early breast cancer with a PDUFA date of July 7, 2026. Label expansions can be meaningful catalysts for large-cap pharma too.

To find upcoming catalysts, use BioPharmCatalyst.com’s FDA calendar. It lists PDUFA dates, trial readouts, and AdCom meetings for free. For trial-level detail, search ClinicalTrials.gov by company name or drug. For conference-driven catalysts, mark your calendar for the major oncology meetings: ASCO (May 29-June 2, 2026, Chicago) and ESMO (October 23-27, 2026, Madrid).

Step 3: Pick a strategy that matches your risk tolerance

Three main approaches to biotech investing:

Catalyst trading: You buy a stock weeks or months before a PDUFA date or trial readout, aiming to capture the run-up and/or the binary event. The highest-risk approach. A successful approval can mean 30-50% gains in a day. A CRL can mean 30-60% losses. You need to be right about the science and the regulatory outcome.

Pipeline investing: You buy and hold a company with multiple drugs in development, betting that the pipeline as a whole generates value over years. Sarepta (SRPT) is a pipeline play: the company has a Duchenne muscular dystrophy gene therapy (Elevidys) on the market plus a broader DMD franchise. Pipeline investors care about platform value, not single catalysts. The risk is lower because one failed drug doesn’t kill the company, but the upside is slower.

Sector rotation: You follow thematic trends across the biotech sector, rotating into whichever sub-sector has the most upcoming catalysts. In 2026, gene therapy and ADCs (antibody-drug conjugates) are the hot themes. You buy a basket of stocks in the theme and ride the sector-wide interest. The most diversified approach but requires staying on top of sector trends.

Step 4: Size your positions for binary risk

This is the step most beginners skip, and it saves your portfolio.

Most biotech FDA catalysts are binary: the stock goes up 30-50% on approval or drops 30-60% on a CRL. Between 2018 and 2022, 37% of NDAs and BLAs received a Complete Response Letter instead of an approval. That’s more than one in three. A CRL is the FDA’s way of saying “not yet”: the drug isn’t approved, and the company needs to address deficiencies before resubmitting. For what a CRL actually says and how to react when one lands on a stock you own, see our guide to Complete Response Letters. If you put 20% of your portfolio in a single pre-PDUFA play and it gets a CRL, you’ve lost 6-12% of your total portfolio on one trade.

The rule: never put more than 2-5% of your portfolio in a single pre-approval biotech position. If you have a $10,000 portfolio, that’s $200-$500 per catalyst play. Yes, a 50% gain on $500 is only $250. But a 60% loss on $500 is $300, not $6,000. You live to trade the next catalyst.

Common mistakes (and what they cost)

Buying the day before the PDUFA date. You’re betting on a coin flip, not investing. The run-up has already happened. If the drug gets approved, the stock can gap up 10% and then sell off as early buyers take profits. If it gets a CRL, you’re down 40-60% instantly. Solution: buy 2-4 weeks before the PDUFA date if you want to trade the catalyst, or buy after the decision if you want to invest in the approved drug.

Ignoring cash burn and dilution. Pre-revenue biotechs burn cash. When they run low, they raise money by selling shares, which dilutes your ownership. A company with 12 months of cash left is one secondary offering away from a 20-30% stock drop. Check the cash runway on the latest quarterly report before buying.

Assuming Phase 2 success guarantees Phase 3 success. It doesn’t. Phase 2 trials are small and sometimes underpowered. A drug that showed a 30% response rate in a 50-patient Phase 2 can show no significant benefit in a 500-patient Phase 3. This is the most common way biotech investors lose money on “promising” drugs.

FOMO buying after the catalyst. The stock is up 80% on FDA approval. You buy at the top. The stock settles back 15-20% over the next week. You’re now underwater on a drug that got approved. If you want to invest post-approval, wait for the dust to settle and evaluate the commercial opportunity, not the approval headline.

Your first biotech trade: a checklist

• You know which phase the drug is in (Phase 1, 2, 3, or approved)
• You know the catalyst date (PDUFA, readout, or AdCom) and it’s 2+ weeks out
• You’ve checked the company’s cash runway (at least 12 months)
• Your position is 2-5% of your total portfolio, no more
• You’ve decided your exit plan before you buy (sell on the catalyst, or hold for the pipeline)
• You understand the binary risk: 37% of FDA applications get a CRL

Start with one catalyst play. Track it. See how the stock behaves before the decision. Learn what a CRL looks like. Biotech investing rewards experience and punishes overconfidence. The stocks don’t care about your thesis. They care about the data.