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January 16, 2026

Welcome to the new era of oncology drug development. Sponsors are moving past traditional dose-finding approaches to using adaptive clinical trial designs in oncology as part of their dose-finding strategy. For years, the efficacy and toxicity of oncology drugs were closely linked. Treatment duration was relatively short, and toxicities were acute. Oncology clinical trials relied on the 3 + 3 design, where doses are escalated until patients experienced toxicity, and then reduced slightly. While this rule-based approach is historically familiar and easy to execute, it is poorly suited for today’s targeted and biologic therapies.

Many newer treatments often reach maximum benefit well before toxicity appears. Patients may stay on treatment for longer periods of time, and the appearance of toxicities is often delayed. Escalating the dose until adverse effects occur can expose patients to unnecessary risks without improving efficacy. Recognizing this, the FDA Project Optimus dose optimization guidance urges sponsors to evaluate multiple doses using all available data sources, including nonclinical, pharmacokinetic, pharmacodynamic, efficacy, and exposure–response information, when selecting a dose for a registrational trial. This comprehensive approach ensures that the dose studied reflects efficacy and safety, rather than relying solely on safety data.

Two charts showing dose–response differences: efficacy and toxicity rise together for cytotoxic drugs, while efficacy plateaus before toxicity for targeted therapies.

Figure 1. The Project Optimus dose optimization guidance changed how we approach drug development and dose justification. The left figure shows dose escalation for a traditional cytotoxic drug where efficacy and toxicity increase in a roughly parallel manner. The right figure depicts dose escalation in a biologic or targeted therapy. The blue shading reflects doses where the dose response for efficacy and toxicity have diverged. Further increases in dose will yield little increased efficacy, but toxicity may continue to increase.

Many organizations are adopting adaptive trial designs that use accumulating data to refine dose selection to meet these expectations. Integrating safety, efficacy, and exposure data in real time allows sponsors to identify the best balance of risk and benefit earlier, improving study efficiency while maintaining statistical and ethical rigor.

Embedding learning into the dose-finding process

Leveraging adaptive clinical trial designs in oncology allows researchers to adjust predefined study elements based on accumulating data, such as dose levels, enrollment ratios, or stopping rules. These approaches embed learning directly into the study, improving efficiency and decision-making confidence.

In dose-finding oncology trials, adaptive methods support real-time assessment of pharmacokinetic (PK), pharmacodynamic (PD), safety, and efficacy data. This allows sponsors to make data-driven decisions during the trial’s progression, instead of waiting until a trial ends to interpret results. As evidence builds, sponsors can refine hypotheses and focus on the most informative doses.

Unlike traditional 3 + 3 designs, which focus only on acute toxicity, adaptive and model-driven approaches capture the broader exposure–response relationship, revealing where benefit plateaus and toxicity begins to rise. This delivers a clearer view of the therapeutic window and a faster path to the optimal dose.

Model-based phase 1 oncology dose-finding trial designs: Defining the biologically effective dose

One of the most effective adaptive strategies is the family of Bayesian Logistic Regression Model (BLRM) designs, which evaluates both dose–toxicity and dose–response relationships using all available data, not just results from the latest cohort.

Rather than escalating until toxicity occurs, this approach identifies a minimum safe and biologically effective dose (MSBED) that achieves the desired pharmacodynamic effect while maintaining safety. This objective is more meaningful than simply finding the Maximum Tolerated Dose (MTD).

Model-based methods reduce exposure to high-risk doses and generate stronger evidence for later-stage development. Regulators increasingly endorse these designs under Project Optimus because they enable more comprehensive dose evaluation, while ethics committees value their ability to minimize patients’ unnecessary exposure to overly toxic doses and maximize what can be learned from every patient.

Category

Basic 3+3 Design

Advanced Model-Driven Design

Dose Levels

Dose levels are fixed, which results in uncertainty around the relevance of selected doses

Dose levels are flexible and chosen by the design to achieve the pre-defined goals

Objective

Identify the maximum tolerated dose

Identify a safe dose with a desired PD profile (minimum safe and biologically effective dose)

Dose Escalation Rules

Driven only by toxicity data (DLT outcomes)

Based on toxicity and PD data to derive the most PD benefit with the least safety risk

Toxicity Issues

Overly toxic dose levels are often selected by the design

Overly toxic dose levels are avoided by applying the EWOC (escalation with overdose control) approach

Adaptive clinical trials in oncology enable learning while treating

Adaptive methods continue to add value in Phase 2/expansion cohort dose-finding studies through a technique known as response-adaptive randomization.

Early in the study, cancer patients are typically randomized equally across active dose arms. As interim analyses reveal new safety and efficacy data, randomization ratios are updated, directing more patients to doses with the most favorable profiles. An independent Data Monitoring Committee (DMC) typically reviews these interim analyses.

Phase 2 Trial

Traditional design

  • Patients are assigned to the 3 dosing arms using a 1:1:1 randomization ratio
  • Many patients are assigned to doses with an undesirable risk-benefit profile, e.g., Doses 1 and 2

This adaptive process ensures that more participants receive potentially effective treatment as the trial progresses, while maintaining statistical control. By study completion, most patients have contributed to the most relevant dose-response data, accelerating learning and confirmation.

Adaptive design with response-adaptive randomization

  • Interim data are examined by an independent data monitoring committee (DMC) to update the randomization ratios
  • Most patients will be assigned to a dose with the best risk-benefit profile, e.g., Dose 3

In oncology programs, where every patient’s experience matters, this approach improves operational efficiency and ethical value, aligning research progress with patient benefit.

Preparing for success in oncology phase 1 trial designs

Adopting adaptive design begins with careful preparation. Before entering first-in-human studies, sponsors need to understand their compound’s pharmacology, its mechanism, receptor targets, and preclinical exposure data. They also need to consider what measurable biomarkers are available to act as indicators of pharmacological activity.

Early exposure–response or PK/PD modeling helps establish the quantitative goals that will guide dose selection as data accumulate. Once initial clinical results are available, clinical trial simulations can compare adaptive and traditional designs to evaluate gains in efficiency, safety, and probability of success.

These simulations provide the evidence needed to refine design choices and build confidence with regulators. By planning early and integrating modeling throughout development, sponsors can streamline decision-making, improve patient safety, and accelerate progress toward the optimal dose.

Adaptive design as the future of oncology development

Adaptive design is now a core element of modern oncology development. By integrating modeling, simulation, and flexible trial structures, sponsors can generate stronger evidence with fewer patients and greater efficiency.

As therapies become more targeted and regulatory expectations evolve, adaptive methods offer a practical path forward, balancing innovation, ethics, and speed. They represent the next step in evidence-based oncology development: smarter trials, better data, and faster access to effective treatments.

FAQs

What is the 3 + 3 clinical trial design for cancer drugs?

The 3 + 3 clinical trial design is a traditional, rule-based method used in Phase I oncology trials to determine the maximum tolerated dose (MTD) of a new cancer drug. This design is popular due to its simplicity and ease of implementation in a clinical setting.

How does the 3 + 3 clinical trial design work?

The 3 + 3 design for clinical trials starts at a very low, safe dose and escalates based on the number of dose-limiting toxicities (DLTs) observed during the first treatment cycle (usually around 4 weeks):

  1. Initial Cohort: Three patients are enrolled and treated at a specific dose level.
  2. Dose Escalation (0 DLTs): If none of the three patients experience a DLT, the next cohort of three new patients is treated at the next higher dose level.
  3. Dose Expansion (1 DLT): If one of the three patients experiences a DLT, three additional patients are enrolled and treated at the same dose level to gather more safety data. The total number of patients at this level is now six.
  4. Dose De-escalation/Stop (2+ DLTs): If two or more patients (out of either the initial three, or the expanded six) experience a DLT, the dose is considered intolerable. The trial stops escalating, and the MTD is defined as the highest dose level at which no more than one out of six patients experienced a DLT.

What does the FDA think about Bayesian clinical trial designs?

The FDA recently issued a draft guidance, Use of Bayesian Methodology in Clinical Trials of Drug and Biological Products. This approach can be helpful for dose finding trials in oncology and can inform drug development for other therapeutic areas too.

How can clinical pharmacologists and biostatisticians help design clinical trials for cancer drugs?

Certara’s clinical pharmacologists and biostatisticians help design cancer drug trials by determining the optimal dose and schedule for safety and efficacy, using modeling and simulation to predict drug behavior in different patient groups (for example, patients who are obese, pregnant, elderly, or pediatric), and optimizing trial designs to include patients with comorbidities (renal, hepatic impairment), or other factors that might influence drug response. They also contribute by analyzing clinical trial samples, developing study protocols, and providing expertise on characterizing a drug’s PK and PD (including its absorption, distribution, metabolism, excretion and biomarker activity).

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Fran Brown, PhD

Vice President, Global Head, Drug Development Science

Fran has over 25 years of experience with strategic and operational global drug development from early discovery to filing and post-marketing.  She possesses a broad knowledge of strategic drug discovery and development, with a special focus on development strategy and the application of model-informed drug development (MIDD).

Blaire Osborn, PhD

Senior Director, Clinical Pharmacology and Translational Medicine

Dr. Osborn has over 25 years of drug development experience in the areas of clinical pharmacology and pharmacokinetics. She has focused primarily oncology and anti-infectives. Before joining Certara, she was a reviewer in the Office of Clinical Pharmacology, US Food and Drug Administration, in the Division of Cancer Pharmacology, CDER where, she participated in the assessment of multiple dose justification submissions under Project Optimus. Prior to working in the FDA, she was a clinical pharmacologist in the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institute of Health (NIH).

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