OnCo
bottlenecksBottleneck

Too many combinations to test

There are thousands of possible drug pairs and sequences. Trials can test a few dozen a year.

With well over a hundred approved oncology agents and hundreds in development, the space of pairwise combinations runs to tens of thousands, and sequences and schedules multiply it further, while the field can run only a few dozen adequately powered combination trials a year. The combinations that are tested are chosen by commercial ownership and precedent rather than biology: thousands of PD-1/PD-L1 combination trials have been launched, most adding an agent to a checkpoint inhibitor without a predictive biomarker. Analyses of historical combination trials suggest that many 'successes' reflect independent action in different patients rather than synergy, which means better patient selection would achieve the same benefit with fewer drugs. Platform trials, factorial and adaptive designs, ex vivo functional testing, and computational prioritisation from dependency maps and combination screens are the only ways to explore the space at a useful rate.

majortrials51 ideas to fix it
How big the problem is
5,683 trials
Clinical trials of PD-1/PD-L1 inhibitors registered by 2021, the large majority as combinations
Most of 15 combinations analysed
Approved combination therapies whose clinical benefit is explained by independent drug action (patient-to-patient variability) without synergy
Root causes
  • Combinatorial growth: n drugs give n(n-1)/2 pairs before doses, schedules and sequences are considered.
  • Companies preferentially combine their own assets and rarely cross-license for early testing.
  • Conventional two-arm trials test one combination each and take years.
  • Preclinical synergy poorly predicts clinical benefit, so prioritisation is weak.
  • Regulatory paths for combinations of two unapproved agents are complex.
What is already being tried
  • I-SPY 2 (Quantum Leap Healthcare Collaborative) and STAMPEDE run adaptive platform trials that add and graduate combination arms continuously.
  • NCI ComboMATCH tests biomarker-directed combinations across cooperative groups.
  • DREAM Challenges and the NCI-DREAM drug combination prediction challenge benchmark computational prioritisation of pairs.
  • The AstraZeneca-Sanger drug combination screen and DepMap provide public combination and dependency data for hypothesis generation.
  • Ex vivo functional testing (organoids, explants, BH3 profiling) is used to select combinations for individual patients.
  • Payload-class switching and dual-payload ADCs address the sequencing problem structurally instead of trial by trial.
What breaking it looks like
Platform trials in each major cancer test dozens of combination arms a year against shared controls, and computational or ex vivo prioritisation has a demonstrated positive predictive value for which combinations succeed in the clinic.

Ideas to fix it

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early clinicalpayersmall cost
A combination pricing rule so two-drug regimens are not priced as two monopolies

When two expensive cancer drugs are combined, the price is often the sum of both even though the extra benefit is smaller. A rule for splitting the total value between them is needed.

speculativepolicysmall cost
A legal right to obtain marketed cancer drugs at cost for combination trials

If a company refuses to supply its approved drug for a well-designed independent trial combining it with a rival's drug, the law would let the trial buy it at manufacturing cost, with results shared back.

early clinicalresearchlarge cost
A neutral platform trial for radiotherapy plus immunotherapy combinations

Radiotherapy may make immunotherapy work better, but the trials to test this are scattered and often small. One shared platform, run by radiotherapy groups with drugs supplied by several companies, would settle it faster.

speculativephilanthropylarge cost
A non-profit phase 1b combination unit that any drug owner can use

Build a shared, not-for-profit clinical unit that runs early combination trials to a standard recipe, so that small companies and academics can test pairs without building their own trial machinery.

speculativeindustrysmall cost
A patent pool for combination method-of-use claims

Companies fear that testing a combination will hand a competitor a patent. A shared pool where combination patents are cross-licensed by default would remove the fear.

being tested at scalephilanthropymedium cost
A permanent neutral non-profit sponsor for multi-company platform trials

Trials that test many companies' drugs side by side against one shared control work best when nobody's company runs them. A standing non-profit sponsor would make this the norm rather than a rare exception.

being tested at scalephilanthropylarge cost
A perpetual platform trial in every major cancer, funded as infrastructure

Instead of starting a new trial for every drug pair, keep one always-open trial per cancer that new arms can join and leave, sharing the same control group.

preclinical evidencephilanthropylarge cost
A public atlas of drug-pair responses across a thousand patient-derived organoids

Build a large, openly shared dataset of how tumour organoids respond to drug pairs, so that anyone can look up which combinations might work for which tumour type.

early clinicalpolicymedium cost
A publicly held library of investigational drugs available for academic combination trials

A government or charity holds stocks of experimental cancer drugs under standing agreements, so academic doctors can test combinations without negotiating with each company separately.

speculativeresearchmedium cost
A real-world sequencing analysis within a year of every new approval

Trials tell us a drug works but not where it fits among the others. Commit to answering 'which order' from hospital data within a year of each approval.

early clinicaldatamedium cost
A registry of every treatment sequence patients actually receive, with outcomes

Record, for every patient, the order of treatments and what happened, so that the most common sequences can be compared and the worst ones flagged.

speculativeindustrysmall cost
A regulator-endorsed standard contract for inter-company combination trials

Most of the delay in testing two companies' drugs together is lawyers negotiating from scratch. A single standard agreement, blessed by regulators, would let them sign in weeks.

early clinicalindustrysmall cost
A standard cross-company combination agreement that takes weeks, not years, to sign

Companies with drugs that might work together rarely test them because the legal negotiation takes longer than the trial. A pre-written standard contract would fix that.

early clinicalresearchlarge cost
A standing platform for testing new drugs with radiotherapy

Radiotherapy is given to half of all cancer patients but few new drugs are tested alongside it. A permanent trial platform would test drug-plus-radiation pairs systematically.

being tested at scalephilanthropylarge cost
A standing platform trial for every major cancer, funded as infrastructure

Rather than building a new trial from scratch for every drug, keep one permanent trial open per cancer where new treatments can be slotted in and dropped out, sharing the same patients, control group and infrastructure.

speculativedatamedium cost
A virtual cancer cell that predicts what a drug will do before you test it

Train a model on millions of experiments where genes and drugs were altered, so it can predict the effect of a new combination without running the experiment.

early clinicalindustrymedium cost
Add the second drug on day one when the escape route is predictable

If most tumours escape a drug by the same back-up route, blocking that route from the start may prevent resistance rather than chase it.

speculativeindustrymedium cost
An oncology patent pool for combination trials across companies

Companies would put their cancer drugs into a shared licensing pool so that any qualified investigator can test combinations of drugs from different owners under one standard agreement, with royalties split by a fixed formula.

preclinical evidenceresearchmedium cost
An open atlas of collateral sensitivity for every approved targeted drug

When a tumour evolves resistance to one drug, it sometimes becomes weaker against another. Map these trade-offs systematically so doctors can pick the next drug to exploit them.

preclinical evidencedatamedium cost
An open engine that ranks every drug pair by predicted synergy before anyone runs a trial

Use existing cell-line and organoid data to score thousands of drug pairs, publish the ranking openly, and only test the top of the list in people.

speculativedatasmall cost
An open forecasting tournament on which combination trials will succeed

Ask experts and models to predict, in public, which registered combination trials will meet their endpoint. Track who is right, and use the best forecasters to decide what to fund.

preclinical evidencephilanthropylarge cost
An open foundation model of the cancer cell trained on perturbation data

Build a shared, openly available AI model that has learned how cancer cells respond to genetic and drug perturbations, so any lab can predict what a new drug or combination might do.

preclinical evidenceresearchlarge cost
Automated combination discovery: patient-sample screens feeding Bayesian platform trials

There are far more possible drug combinations than can ever be tried in patients. Test thousands on living samples of real tumours, then feed only the winners into adaptive trials.

preclinical evidenceresearchmedium cost
Combination baskets defined by resistance mechanism rather than by cancer type

Group patients by why their last drug stopped working, then test the combination designed to fix that specific failure, whatever the cancer.

preclinical evidenceresearchmedium cost
Design drug pairs where resisting one makes you vulnerable to the other

Choose two treatments so that whatever the tumour does to escape the first, it becomes easier to kill with the second. The immune system is a good candidate partner.

early clinicaldatasmall cost
Emulate combination trials from real-world data to triage which ones to run

Many combinations are already used off-label. Careful analysis of what happened to those patients can rule out the pairs that clearly do not help before spending money on trials.

speculativeregulatorsmall cost
Every approved cancer drug ships with a public combination-readiness data pack

Require that approved cancer drugs come with a standard set of data (blood levels, drug interactions, toxicity profile) so anyone can design a safe combination trial without asking the company.

speculativeindustrymedium cost
Factorial dose finding for drug combinations instead of full dose of everything

When two cancer drugs are combined, each is usually given at its full single-agent dose, which often proves too toxic. Testing a grid of dose pairs would find combinations that work with tolerable side effects.

early clinicalresearchlarge cost
Factorial trials that test several cheap generics at once in the adjuvant setting

One large trial can test aspirin, a statin, metformin and exercise at the same time by randomising each separately, answering four questions for the price of one.

early clinicalregulatormedium cost
Find the lowest effective doses of both drugs in a combination, not the highest tolerated

Combination trials usually keep one drug at full dose and push the other as high as patients can bear. Testing a grid of dose pairs would find combinations that work at lower, safer doses.

preclinical evidenceresearchmedium cost
Grow each trial patient's tumour as organoids to decide which platform arm opens next

While patients are treated in a platform trial, their tumour cells grow in a dish and are tested against dozens of drug pairs. The pairs that win in the dish become the next arms.

early clinicalengineeringmedium cost
Implant a tiny device that tests twenty drugs inside the patient's own tumour

A rice-grain-sized implant can release small doses of many different drugs into separate spots of a tumour, then be removed so doctors can see which one worked in that person.

speculativeresearchmedium cost
In silico trials to prioritise combinations, scored against later real trials

Simulate trials of drug combinations in populations of virtual patients to decide which real trials to run, and keep score of how often the simulations were right.

early clinicalresearchmedium cost
Kill combination arms early using circulating tumour DNA, before waiting for scans

A blood test at six weeks can show whether a treatment is doing anything. Trials should use it to drop failing combinations fast and move patients on.

early clinicalresearchmedium cost
Let the trial learn: response-adaptive allocation across many combination arms

As results come in, the trial sends more new patients to the arms that are working and fewer to those that are not, so more people benefit and bad arms die faster.

speculativeregulatormedium cost
Make paediatric combination studies part of every relevant adult cancer drug approval

Children's cancers are treated with combinations, but companies study new drugs in children one at a time. Approvals should require the combination study children actually need.

early clinicalindustrymedium cost
Mechanistic computer models to pick combination doses before dosing patients

Simulate how two drugs interact in the body and the tumour to pick a starting dose and schedule, instead of guessing from single-drug data.

early clinicalregulatorsmall cost
No accelerated approval for a combination without proof each part contributes

Regulators should refuse to approve a two-drug combination unless there is evidence that both drugs are doing something, so patients are not exposed to useless extra toxicity and cost.

early clinicalregulatorsmall cost
One ethics approval and one consent form for a platform trial across countries

Adding a new arm to an international platform trial currently needs approval in every country again. A single, pre-agreed process would let arms open in weeks.

speculativepayermedium cost
Payers cover off-label combinations only inside registry-randomised trials

Insurers already pay for many untested drug combinations. Paying only when the patient joins a simple randomised comparison would turn that spending into evidence.

being tested at scaleresearchlarge cost
Pre-surgery platform trials that test combinations on pathological response in months

Give combinations before surgery and look at how much tumour is left when it is removed. That answer comes in months, so many pairs can be tested quickly.

speculativeclinicmedium cost
Registry-embedded randomisation of treatment order in routine care

When two approved drugs are both reasonable next steps and nobody knows which should come first, let the clinic flip a coin and record what happens.

speculativeresearchmedium cost
Rotate between drugs on a fixed schedule instead of waiting for failure

Hospitals rotate antibiotics to stop bacteria adapting. Cycling between two cancer drugs on a set schedule, rather than using one until it fails, might work the same way.

speculativeresearchlarge cost
Sequential multiple-assignment randomised trials to find the best order of ADCs

Patients are randomised at each decision point, not just at the start, so one trial can compare whole treatment sequences rather than single drugs.

early clinicalregulatormedium cost
Shared concurrent control arms across sponsors' trials in the same setting

When five companies each run a trial against the same standard treatment in the same patients, let them pool the standard-treatment patients so fewer people are randomised to the old drug.

preclinical evidenceresearchmedium cost
Test alternating drug schedules against giving both drugs at once

Two drugs might work better given in turns rather than together, with less toxicity. Almost no trial has tested this.

preclinical evidenceresearchmedium cost
Time immunotherapy to the moment targeted drugs make tumours visible

Targeted drugs briefly make cancer cells easier for the immune system to spot. Giving immunotherapy exactly in that window, rather than at the same time, may work better.

early clinicalresearchmedium cost
Two-week pre-operative windows to compare combination biology head to head

Give patients a short course of one of several drug pairs in the gap before surgery and compare what happened inside the tumours. It is the fastest human test of whether a combination does anything.

early clinicalresearchmedium cost
Unmask hidden antigens with a short epigenetic course before immunotherapy

Low doses of drugs that change how DNA is packaged can make cancer cells display more of what marks them as abnormal, potentially waking up immunotherapy in cold tumours.

early clinicaldatasmall cost
Watch routine care for drug combinations that quietly make cancer treatment worse

Some everyday medicines, such as antibiotics or steroids, seem to blunt immunotherapy. Automatically scanning health records for such harmful pairs would catch them years earlier.

speculativeresearchlarge cost
Whole-patient digital twins validated in prospective randomised trials

Build a computer model of each patient's cancer and body that simulates how different treatments would go, and prove in a proper trial that choosing treatment with the model helps.

Key papers

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rctNew England Journal of Medicine 2025changed practice
AMPLIFY: fixed-duration acalabrutinib plus venetoclax, with or without obinutuzumab, versus chemo-immunotherapy in fit CLL patients

AMPLIFY delivered the first all-oral, fixed-duration doublet for front-line CLL and supported its approval, giving fit patients a way to avoid both chemotherapy and years of continuous BTK inhibitor. It does not settle whether a doublet or triplet is best, or how AV compares with venetoclax-obinutuzumab. Patients with TP53 aberration were excluded and still need different strategies.

rctNew England Journal of Medicine 2025changed practice
BREAKWATER: encorafenib plus cetuximab with chemotherapy as first treatment for BRAF V600E-mutated colorectal cancer

Patients with newly diagnosed metastatic colorectal cancer whose tumour carries a BRAF V600E mutation, which is about 8-12% of cases, should now be offered encorafenib and cetuximab together with FOLFOX from the start rather than after chemotherapy fails; median survival has roughly doubled to about two and a half years. BRAF testing at diagnosis is therefore essential, alongside RAS and mismatch repair testing. The regimen is more toxic than chemotherapy alone.

rctNew England Journal of Medicine 2024changed practice
EV-302: enfortumab vedotin plus pembrolizumab replaces chemotherapy as first treatment for advanced bladder cancer

Almost every patient newly diagnosed with advanced bladder or urothelial cancer should now be offered enfortumab vedotin plus pembrolizumab rather than chemotherapy, with median survival extended from about 16 months to over two and a half years. Neuropathy and skin toxicity need monitoring and dose adjustment, and patients with severe diabetes or pre-existing neuropathy need care. Platinum chemotherapy remains an option for those who cannot receive the combination.

rctThe Lancet 2023changed practice
SPOTLIGHT: zolbetuximab, the first Claudin 18.2 antibody, added to chemotherapy in gastric cancer

Patients with newly diagnosed advanced stomach cancer should now have Claudin 18.2 tested alongside HER2, PD-L1 and mismatch repair, because roughly a third will be eligible for zolbetuximab, which adds about three months of median survival. The main practical problem is nausea and vomiting during infusions, which needs aggressive prophylaxis. How to sequence or combine it with immunotherapy in PD-L1-positive tumours is unresolved.

rctNew England Journal of Medicine 2022changed practice
RELATIVITY-047: relatlimab plus nivolumab, the first LAG-3 checkpoint combination, in untreated advanced melanoma

Patients with newly diagnosed advanced melanoma have a dual-checkpoint option that improves on nivolumab alone with only a modest increase in serious side effects, making it attractive for those unable to tolerate or unwilling to risk the toxicity of ipilimumab. It did not prove superior survival, and it has not been compared with nivolumab plus ipilimumab, which remains preferred for patients with brain metastases or other high-risk features. LAG-3 is now an established target under study in many other cancers.

rctNew England Journal of Medicine 2021changed practice
CLEAR: lenvatinib plus pembrolizumab versus sunitinib as first treatment for advanced kidney cancer

Patients with newly diagnosed advanced clear-cell kidney cancer should receive an immunotherapy-based combination; lenvatinib plus pembrolizumab gives the highest response rate and longest PFS of the available options, at the cost of more side effects requiring dose adjustment. Sunitinib alone is no longer an appropriate standard. Choosing among the combinations depends on risk group, symptoms, comorbidity and the value placed on treatment-free survival, which favours nivolumab plus ipilimumab in intermediate and poor risk.

rctNew England Journal of Medicine 2020changed practice
IMbrave150: atezolizumab plus bevacizumab replaces sorafenib as first treatment for advanced liver cancer

Patients with advanced liver cancer and good liver function should be offered atezolizumab plus bevacizumab (or durvalumab plus tremelimumab) rather than sorafenib as first treatment; median survival is now around 19 months and about a quarter of patients respond. Endoscopy to treat varices before starting bevacizumab is essential because of bleeding risk. Patients with poorer liver function (Child-Pugh B) or autoimmune disease or transplants were not studied.

reviewCell 2000
The Hallmarks of Cancer: six capabilities every tumour must acquire

The hallmarks are the mental map most oncologists and researchers use to think about what cancer is and where drugs act. A newcomer can understand nearly every therapy as an attack on one hallmark: kinase inhibitors on proliferative signalling, checkpoint blockade on immune evasion, anti-VEGF drugs on angiogenesis.

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A combination pricing rule so two-drug regimens are not priced as two monopoliesA legal right to obtain marketed cancer drugs at cost for combination trialsA neutral platform trial for radiotherapy plus immunotherapy combinationsA non-profit phase 1b combination unit that any drug owner can useA patent pool for combination method-of-use claimsA permanent neutral non-profit sponsor for multi-company platform trialsA perpetual platform trial in every major cancer, funded as infrastructureA public atlas of drug-pair responses across a thousand patient-derived organoidsA publicly held library of investigational drugs available for academic combination trialsA real-world sequencing analysis within a year of every new approvalA registry of every treatment sequence patients actually receive, with outcomesA regulator-endorsed standard contract for inter-company combination trialsA standard cross-company combination agreement that takes weeks, not years, to signA standing platform for testing new drugs with radiotherapyA standing platform trial for every major cancer, funded as infrastructureA virtual cancer cell that predicts what a drug will do before you test itAdd the second drug on day one when the escape route is predictableAn oncology patent pool for combination trials across companiesAn open atlas of collateral sensitivity for every approved targeted drugAn open engine that ranks every drug pair by predicted synergy before anyone runs a trialAn open forecasting tournament on which combination trials will succeedAn open foundation model of the cancer cell trained on perturbation dataAutomated combination discovery: patient-sample screens feeding Bayesian platform trialsCombination baskets defined by resistance mechanism rather than by cancer typeDesign drug pairs where resisting one makes you vulnerable to the otherDual-payload ADCs in first line to prevent resistanceEmulate combination trials from real-world data to triage which ones to runEvery approved cancer drug ships with a public combination-readiness data packFactorial dose finding for drug combinations instead of full dose of everythingFactorial trials that test several cheap generics at once in the adjuvant settingFind the lowest effective doses of both drugs in a combination, not the highest toleratedGrow each trial patient's tumour as organoids to decide which platform arm opens nextImplant a tiny device that tests twenty drugs inside the patient's own tumourIn silico trials to prioritise combinations, scored against later real trialsKill combination arms early using circulating tumour DNA, before waiting for scansLet the trial learn: response-adaptive allocation across many combination armsMake paediatric combination studies part of every relevant adult cancer drug approvalMechanistic computer models to pick combination doses before dosing patientsNo accelerated approval for a combination without proof each part contributesOne ethics approval and one consent form for a platform trial across countriesPatient-derived organoids to pick ADC payloadsPayers cover off-label combinations only inside registry-randomised trialsPayload-class switching as the rule for ADC sequencingPre-surgery platform trials that test combinations on pathological response in monthsRegistry-embedded randomisation of treatment order in routine careRotate between drugs on a fixed schedule instead of waiting for failureSequential multiple-assignment randomised trials to find the best order of ADCsShared concurrent control arms across sponsors' trials in the same settingTest alternating drug schedules against giving both drugs at onceTime immunotherapy to the moment targeted drugs make tumours visibleTwo-week pre-operative windows to compare combination biology head to headUnmask hidden antigens with a short epigenetic course before immunotherapyWatch routine care for drug combinations that quietly make cancer treatment worseWhole-patient digital twins validated in prospective randomised trials

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