How to Read Clinical Trial Results 2025 — Educational Guide | Merlintrader trading Blog

How to Read Clinical Trial Results 2025

Educational guide to Phase 1/2/3 data, endpoints, statistics and safety signals

Reading time: 12–15 minutes | Words: 3,500+

Educational only: this chapter does not provide investment advice, trading signals or guarantees of results. Any decision to buy, sell or hold a security remains entirely your responsibility.

1. Why clinical trial results matter for investors and traders

Clinical trial readouts are among the most impactful events in biotech. A positive Phase 3 trial can re-rate a company, while a failed trial can remove most of the equity value in a single session. Price moves of plus or minus 40–80 percent around major readouts are not unusual in small and mid-cap names.

Many market participants only read the headline of the press release. However, the market reaction is often driven by the details: which endpoints were met, how robust the statistics are, how clean the safety profile looks and what the results imply for real patients. This chapter focuses on those details.

Key idea: a trial result is not just “good” or “bad”. It is a complex data package. The more nuance you can see in that package, the better you can understand why the market reacts the way it does.

2. Understanding clinical trial phases

Phase Participants Typical duration Main goal Indicative market impact Role in development
Phase 1 20–100 healthy volunteers or patients 1–2 years Safety, tolerability and dose finding Usually modest (about ±10–20%) Exploratory, early assessment
Phase 2 100–500 patients 2–3 years Initial efficacy signals and safety Medium impact (about ±20–50%) Proof-of-concept for larger trials
Phase 3 1,000–5,000 patients (sometimes more) 2–3 years Confirm efficacy and monitor adverse reactions Highest impact (about ±30–80%) Key evidence package for regulators
Phase 4 Patients in real-world use Ongoing after approval Long-term safety and additional outcomes Typically modest (about ±5–15%) unless safety issues arise Refines label and risk–benefit profile

Why Phase 3 attracts so much attention

Phase 3 trials are often described as “make-or-break” because they provide the main evidence package that regulators use to decide on approval. A clearly positive Phase 3 with good safety can unlock a marketing authorisation. A negative Phase 3 result can halt a program entirely.

Perspective: early-phase data can move share prices, but Phase 3 is where the drug is asked to perform under rigorous conditions in a large, representative population. For many small companies, the outcome of a single Phase 3 can decide their medium-term future.

3. Primary vs secondary endpoints

Endpoints are the specific outcomes a trial is designed to measure. Understanding which are primary and which are secondary is essential to interpret a result correctly.

Primary endpoints

  • Main measure of efficacy that the trial is statistically powered to detect.
  • Defined in advance in the protocol and agreed with regulators.
  • Usually must reach statistical significance for the trial to be considered successful.
  • If the primary endpoint is not met, the study is generally considered negative, regardless of some secondary findings.

Secondary endpoints

  • Additional measures of efficacy or patient benefit, such as quality-of-life scores or reduction in hospitalisations.
  • Not individually powered to the same extent as the primary endpoint.
  • Can strongly influence how attractive the drug is for regulators, physicians and payers.
  • A trial that meets its primary endpoint but misses important secondary endpoints is technically “positive”, yet the commercial and regulatory outlook can become more uncertain.

Safety data

  • Includes adverse events, serious adverse events, discontinuations and deaths.
  • Even very effective drugs can be held back if the safety profile is not acceptable for the intended population.
  • Patterns such as high discontinuation rates or organ toxicity are carefully scrutinised by regulators and clinicians.
Case study – AGIO RISE UP (November 2025):
In the RISE UP trial for sickle-cell disease, the primary endpoint related to haemoglobin response was formally met, but key secondary endpoints linked to painful crises and fatigue did not show convincing improvement. Safety was broadly acceptable. The market nevertheless reacted with a sharp drawdown, reflecting concern that the data package might not demonstrate enough real-world clinical benefit for regulators and prescribers.

4. Statistical significance and p-values

Clinical trials are built on statistics. A result can look impressive in absolute terms but still be considered inconclusive if it could easily be explained by random variation.

What a p-value represents

  • The p-value expresses the probability that the observed difference between treatment and control occurred by chance, assuming the drug has no true effect.
  • By convention, a p-value below 0.05 is often taken as “statistically significant”, meaning the result is unlikely to be due to chance alone.
  • A p-value above 0.05 suggests the trial did not provide enough evidence to reject the “no effect” hypothesis.
Scenario Observed effect P-value Interpretation
Clear positive Strong reduction in symptom score vs placebo 0.001 Highly unlikely to be random; strong statistical support.
Borderline Modest improvement vs placebo 0.048 Formally significant but close to the threshold; usually analysed with caution.
Inconclusive Minimal difference vs placebo 0.15 Result consistent with random noise; trial generally considered negative.
Practical note: headlines sometimes highlight “near misses” such as p=0.06. From a strict statistical standpoint these results are not significant, even if the company presentation may try to emphasise trends.

5. Safety data and red flags

Safety can be decisive. A highly effective drug with severe toxicity may still struggle to obtain approval or adoption, especially if safer alternatives exist.

Potential red flags

  • Imbalances in deaths between treatment and control arms judged to be drug-related.
  • Serious organ toxicities or life-threatening adverse events at therapeutic doses.
  • High rates of treatment discontinuation due to side effects.
  • Safety issues that prevent use of doses needed to achieve efficacy.
  • Problematic interactions with common background therapies.

Elements that support a positive view

  • Side-effect profile similar to or better than existing standard of care.
  • Low discontinuation rates, indicating that patients can stay on therapy.
  • Adverse events that are mild, predictable and manageable in clinical practice.

6. Real-world examples

NUVB and IBTROZI

  • Program: development of IBTROZI for polycythaemia vera.
  • Data: pivotal trials showed meaningful improvements in key disease measures and supportive secondary outcomes.
  • Safety: manageable profile judged acceptable for the target population.
  • Regulatory outcome: approval in 2025, followed by encouraging early commercial uptake.
  • Market takeaway: a combination of clear efficacy, acceptable safety and a well-executed launch can sustain positive share-price trends beyond the initial approval day.

AGIO and the RISE UP trial

  • Program: treatment for sickle-cell disease.
  • Data: primary endpoint in terms of haemoglobin response met, but important secondary endpoints related to clinical crises and fatigue did not show compelling benefit.
  • Safety: broadly acceptable, but efficacy profile raised questions on differentiation and real-world value.
  • Market takeaway: even when a primary endpoint is technically positive, lack of clear clinical benefit on key outcomes can lead to a negative re-rating.

7. Market and trading implications (descriptive)

The following points summarise how many active biotech traders tend to approach clinical-trial catalysts. They are observations of market behaviour, not recommended strategies.

Common patterns in market behaviour

  • Trial dates are often tracked months in advance using specialised calendars and company guidance.
  • As expectations build, some stocks experience a “run-up” in the weeks before data, especially when sentiment is optimistic.
  • On data day, spreads widen and intraday volatility increases sharply; price reactions can be outsized in both directions.
  • In the days after the announcement, the market frequently revisits the first move as analysts digest full datasets, conference-call commentary and competitor reactions.

Risk-focused practices used by some traders

  • Limiting exposure to any single binary event to a small portion of total capital (for example a few percent of the overall portfolio).
  • Reducing or closing positions before the readout, focusing on the pre-event move rather than the outcome itself.
  • Waiting for at least one or two trading sessions after the data release before considering new positions, to let the initial emotional reaction settle.

These practices are not universally appropriate and may not suit your objectives or risk tolerance. They are described solely to illustrate how some market participants choose to manage the risk of binary events.

8. Trial-results checklist

When a new press release drops, a simple checklist can help structure the analysis:

  • Was the primary endpoint met, and with what p-value?
  • Which secondary endpoints were positive, negative or exploratory only?
  • Does the safety profile look acceptable for the disease and available alternatives?
  • Was the patient population representative of the real-world setting?
  • Is the trial size adequate to support robust conclusions?
  • Is the comparator (placebo or active control) appropriate?
  • Do company comments and guidance suggest a clear regulatory path?
  • How large is the addressable market and how crowded is the competitive landscape?
  • Does the company have sufficient cash to reach the next milestones?

Conclusion: building a disciplined way to read trial data

Reading clinical trial results carefully is one of the core skills for anyone interested in biotech. The goal is not to predict the future with certainty, but to understand what the data really show and how regulators, physicians and investors are likely to interpret them.

Primary and secondary endpoints, statistical robustness and safety all play a part. Looking at these elements together, rather than relying on a single headline, can help avoid many of the common pitfalls seen around major catalysts.

Always cross-check trial information with primary sources such as full press releases, company presentations, regulatory documents and peer-reviewed publications. Consider seeking professional advice before taking financial decisions based on trial outcomes.

Biotech Catalyst Calendar

This lesson is part of a broader educational series on catalyst-driven biotech investing. To explore upcoming trial readouts and regulatory events, you can consult the dedicated calendar on Merlintrader.

Open the Biotech Catalyst Calendar

Scanner for active traders

Try ChartsWatcher free, then unlock 10% OFF with SAVE10

ChartsWatcher is a real-time scanner for momentum traders: fast movers, unusual volume and rotations — so you can focus on the few tickers that matter right now, instead of watching hundreds of charts.

Start with the free version. When you upgrade, use SAVE10 for 10% OFF your first paid period.

Start free – then use SAVE10

No credit card required to start. Apply SAVE10 when upgrading.

Recommended platform

One platform. All your brokers.

Medved Trader connects multiple brokers in one workspace, with pro charts, hotkeys and fast execution — without changing your broker accounts.

A single cockpit for positions, Level II and multi-broker order routing, built for active day & swing traders.

Get 1 Month Free ➔

Multi-broker workflow + customizable layouts in one platform.

Monica.im Monica.im – the AI assistant I use every day
If you find value in the work I publish on Merlintrader and want a practical AI assistant for research and writing, you can sign up using this referral link. Click here to try Monica.im and support the site

Find out how I use AI on Merlintrader: AI, retail and Merlintrader

Disclosure: some of the links in the promotional blocks above are affiliate or referral links. If you choose to subscribe or sign up through them, Merlintrader may receive a small commission or benefit at no extra cost to you.