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.
- 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.
- 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Group patients by why their last drug stopped working, then test the combination designed to fix that specific failure, whatever the cancer.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Insurers already pay for many untested drug combinations. Paying only when the patient joins a simple randomised comparison would turn that spending into evidence.
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.
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.
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.
Patients are randomised at each decision point, not just at the start, so one trial can compare whole treatment sequences rather than single drugs.
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.
Two drugs might work better given in turns rather than together, with less toxicity. Almost no trial has tested this.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Pages like this
not linked directly; found by shared links- BottleneckPreclinical models that do not predict people
Shares Two-week pre-operative windows to compare combination biology head to head, Whole-patient digital twins validated in prospective randomised trials, A virtual cancer cell that predicts what a drug will do before you test it, Automated combination discovery: patient-sample screens feeding Bayesian platform trials.
- BottleneckSecrecy and intellectual property block collaboration
Shares A patent pool for combination method-of-use claims, A regulator-endorsed standard contract for inter-company combination trials, A legal right to obtain marketed cancer drugs at cost for combination trials, Every approved cancer drug ships with a public combination-readiness data pack.
- BottleneckAcquired resistance to every therapy
Shares Rotate between drugs on a fixed schedule instead of waiting for failure, Test alternating drug schedules against giving both drugs at once, An open atlas of collateral sensitivity for every approved targeted drug, Combination baskets defined by resistance mechanism rather than by cancer type.
- BottleneckTrial design, endpoints and cost
Shares In silico trials to prioritise combinations, scored against later real trials, Let the trial learn: response-adaptive allocation across many combination arms, A standing platform trial for every major cancer, funded as infrastructure, Kill combination arms early using circulating tumour DNA, before waiting for scans.
- IdeaA drug screen that only rewards killing sleeping cancer cells
Shares DrugBank & ChEMBL, DepMap (Cancer Dependency Map), Functional (ex vivo) drug testing, CRISPR functional genomics.