Biotech Stock Screener: 7 Filters That Work

Most stock screeners are built for regular companies. You filter by P/E ratio, revenue growth, dividend yield. These filters are useless for biotech, where 60% of public companies have zero revenue and negative earnings. If your screener has a P/E filter, close it and start over.

A biotech screener needs different inputs: catalyst proximity, cash runway, insider buying clusters, institutional ownership trends, short interest, and market cap relative to pipeline stage. Here are the 7 filters that actually separate tradeable biotech setups from dead money.

Step 1: Catalyst within 6 months

A biotech stock without a data readout, PDUFA date, or earnings catalyst within 6 months is dead money. The stock will drift. Your capital sits idle.

How to screen: Go to ClinicalTrials.gov and search for the company’s lead drug. Look at the “Estimated Study Completion Date.” For PDUFA dates, use BioPharmCatalyst.com or the FDA advisory committee calendar.

If you can’t find a catalyst within 6 months, skip the stock. There are 800+ biotech companies. You don’t need to bet on one with nothing happening.

Threshold: Catalyst within 6 months, confirmed by a public source. “Management expects data in H2” doesn’t count. ClinicalTrials.gov completion dates or FDA-posted PDUFA dates are the standard.

Step 2: Cash runway over 18 months

For pre-revenue biotechs, cash is the only number that matters until they have a product.

Formula: (Cash + Short-term investments) ÷ (Operating cash flow × -1 per quarter) = runway in quarters. Find these numbers in the latest 10-Q on SEC EDGAR.

Thresholds:

Under 12 months: dilution is certain, probably within 90 days. Avoid.
12–18 months: dilution is likely. Management is waiting for a catalyst window.
Over 24 months: buffer exists. The company can survive a trial failure.

Red flag: A biotech with great science and 8 months of cash is not an investment. It’s a bet that the secondary offering happens after your entry. Secondary offerings typically drop the stock 20–30% on announcement.

Step 3: Market cap relative to catalyst size

A $200M market cap biotech with a PDUFA for a $2B market opportunity is a favorable setup. A $5B market cap biotech with Phase 1 data and no catalyst for 2 years is dead money.

Calculate the rough “catalyst value / market cap” ratio. If the drug succeeds, what’s the addressable market? If the market cap already prices in approval, the upside is limited and the downside is the full binary CRL risk. See the guide on biotech valuation methods for the rNPV framework.

Real example: BridgeBio (BBIO) has a ~$16.5B market cap with Attruby generating ~$722M annually and BBP-418 awaiting an November 2026 PDUFA. At that valuation, approval is mostly priced in. A CRL, which happens to 37% of applications, would crater the stock 40–60%. The risk-reward is asymmetric in the wrong direction.

Step 4: Insider buying clusters, not single purchases

Biotech insiders buy for exactly one reason: they think the stock is going up. They sell for dozens of reasons (diversification, divorce, tax planning, 10b5-1 automatic plans). The challenge is separating the signal from the noise.

The hierarchy of insider buys:

Cluster buying: 3+ insiders buying within 30 days at market prices. This is the highest-conviction signal in biotech.
Large CEO/CSO purchase: $500K+ open market buy by the CEO or Chief Scientific Officer. They know the data.
First-ever purchase: An insider who has never bought before suddenly buys.
Small director purchase: Board members buying $25K. Weak signal. Directors have less visibility than C-suite.

What is NOT a signal: Option exercises (exercising and holding is neutral; exercising and immediately selling is bearish), 10b5-1 plan sales (pre-scheduled, tells you nothing), tax withholding sales.

Where to screen: OpenInsider is free and shows real-time Form 4 filings. Filter for “P - Open market or private purchase” and ignore “A - Grant, award, or other acquisition.” Cross-reference with the catalyst calendar: insider buying 3–6 months before a PDUFA date is the ideal setup.

Step 5: Institutional ownership trend

Rising institutional ownership over the last 2 quarters, especially from biotech-specialist funds (OrbiMed, RA Capital, Frazier, venBio, Baker Bros), is confirmation. Declining institutional ownership with a flat stock price means smart money is exiting.

Check 13F filings on WhaleWisdom or SEC EDGAR. Look at the last 2 quarters specifically. A single quarter of institution selling could be noise. Two consecutive quarters is a trend.

Step 6: Short interest as percentage of float

High short interest (over 15% of float) means potential for a short squeeze on a positive catalyst. But high short interest with no near-term catalyst means the shorts are right. This filter only works combined with Filter 1 (catalyst proximity).

Check short interest on MarketBeat or your brokerage platform. Most platforms update short interest data twice monthly.

Real example setup: Insider cluster buying + 15%+ short interest + PDUFA within 8 weeks = short squeeze candidate. Insider buying + 3% short interest + no catalyst for 12 months = accumulation, not a squeeze trade.

Step 7: Volume and options activity

Unusual options activity (high call volume relative to open interest) in the 2–4 weeks before a PDUFA date or data readout signals accumulation. Low volume with no options activity means nobody is positioned for the event, including you.

Use Barchart Unusual Options Activity or the options chain on your brokerage platform. Look for call volume 3x+ open interest with near-the-money strikes expiring after the catalyst date.

Common mistakes

Screening without a catalyst filter. You’ll get a list of 50 “cheap” biotech stocks with no events for 12 months. All of them are dead money.

Using a single filter in isolation. High short interest without a catalyst means the shorts are right. Insider buying without cash runway means dilution is coming before the catalyst hits. Every filter works better in combination.

Trusting the screener output without manual review. A screener gives you a shortlist of 8–12 names. You still need to read the trial design, check the primary endpoint on ClinicalTrials.gov, and verify the PDUFA date hasn’t slipped. The screener narrows 800 stocks to 12. Your brain does the rest.

Ignoring the market cap filter. A $50M micro-cap with a catalyst is not a safer bet than a $500M small-cap. Micro-caps have wider spreads, lower liquidity, and management teams that may have never filed an NDA or BLA.

Final checklist

Catalyst within 6 months, confirmed on ClinicalTrials.gov or FDA calendar
Cash runway over 18 months (from 10-Q)
Market cap doesn’t already price in approval
Insider cluster buying or large CEO purchase (OpenInsider)
Institutional ownership rising over last 2 quarters (WhaleWisdom)
Short interest cross-referenced with catalyst proximity (MarketBeat)
Options activity confirms positioning (Barchart)

For the broader investing framework these filters feed into, see how to invest in biotech stocks and the Q3 2026 FDA calendar for current PDUFA dates.