Every targeted therapy needs a way to find the patients it will help, and that is what a companion diagnostic does. As precision medicine has become the dominant paradigm in oncology and spread into other areas, companion diagnostics have moved from a regulatory obligation to a strategic asset, and the partnerships between drug developers and diagnostic companies have become central to how modern therapies reach market. Here is a guide to the leading companies and how these partnerships work.
What a companion diagnostic actually does
A companion diagnostic is a test that identifies the patients who are likely to benefit from a specific therapy, typically by detecting a biomarker such as a genetic mutation or protein expression. It is what makes precision medicine possible: without the test, you cannot reliably find the responders, and the drug’s benefit gets diluted across an unselected population. The category is now central to oncology, where tests identify patients eligible for targeted therapies across a wide range of mutations and pathways, and it is expanding as biomarker-driven treatment spreads to other diseases.
The major players
- Roche, including Foundation Medicine, holds one of the largest companion diagnostics franchises, spanning tissue-based testing and comprehensive genomic profiling, and its combination of diagnostics and pharma under one roof is a distinctive strategic position.
- Thermo Fisher is a major force with a broad testing portfolio and extensive pharma partnerships.
- Agilent is a long-established leader, particularly strong in tissue-based assays.
- Guardant Health has built a leading position in liquid biopsy, using blood-based testing to detect actionable tumor mutations, an approach that avoids the need for tissue and is increasingly important.
- Illumina, QIAGEN, and Abbott are all substantial participants across sequencing-based and molecular testing.
- Myriad Genetics, NeoGenomics, Caris Life Sciences, Natera, and Exact Sciences hold notable positions across genomic profiling, oncology testing, and specialized diagnostics.
How the pharma partnerships work
The defining feature of this field is co-development: a drug developer and a diagnostic company work together so that the test is developed, validated, and approved alongside the therapy, ideally reaching market at the same time. This requires early coordination, since the diagnostic needs to be ready to identify patients for the pivotal trial, and the regulatory pathways for the drug and the test must be aligned. For a drug developer, choosing a diagnostic partner is therefore a strategic decision made early in development, not a late-stage procurement exercise, and the partner’s regulatory experience, platform, and commercial reach directly affect whether the therapy can actually find its patients after approval.
What is changing
Several shifts matter. Next-generation sequencing is growing fastest among testing approaches, driven by demand for comprehensive genomic profiling that assesses many biomarkers at once rather than testing them one by one. Liquid biopsy continues to expand, offering blood-based testing that avoids the difficulty of obtaining tissue. And the regulatory environment is evolving, with US regulators having proposed reclassifying certain sequencing-based oncology companion diagnostics in a way that could shorten their path to market, a change that would meaningfully affect development timelines if it proceeds.
How to choose a companion diagnostics partner
For a drug developer, the criteria are specific. Prioritize regulatory track record in getting companion diagnostics approved alongside therapies, since this is where partnerships most often stumble. Assess platform fit for your biomarker, whether it needs tissue-based testing, sequencing, or liquid biopsy. Consider commercial reach and market access, because a test that is approved but not widely available or reimbursed cannot find your patients in practice. Weigh their co-development experience and willingness to work to your timeline. And engage early, because a diagnostic that arrives late can delay a drug’s launch or blunt its uptake.
The bottom line
Companion diagnostics are the infrastructure that makes precision medicine work, and the field is led by Roche and Foundation Medicine, Thermo Fisher, Agilent, Guardant, Illumina, QIAGEN, and Abbott, alongside strong specialists. For a drug developer, the diagnostic partner is a strategic choice with real consequences for regulatory timing, patient identification, and commercial uptake, and it deserves to be made early and carefully. Choose for regulatory experience, platform fit, and genuine commercial reach, and coordinate the diagnostic and the drug as one program rather than two.
The commercial problem nobody plans for
The failure that most often undermines a companion diagnostic is not scientific or regulatory but commercial, and it is worth spelling out because it catches so many drug developers by surprise. A companion diagnostic can be technically excellent, rigorously validated, and duly approved, and still fail to do its job, because clinicians cannot easily order it, laboratories do not run it, or payers will not reimburse it. If the test is not available and paid for in ordinary clinical practice, physicians will not test, untested patients will not be identified, and your drug will not reach the people it could help, regardless of how good both the drug and the test are. This is a real and recurring problem in precision medicine, and it means market access for the diagnostic is not a secondary concern but a core determinant of your therapy’s commercial success. Planning for it means asking, early, how the test will actually reach clinical practice: which laboratories will run it, how clinicians will order it, what the reimbursement pathway is, and what evidence payers will require to cover it. It means choosing a diagnostic partner with genuine commercial reach and market access capability, not just technical and regulatory competence, and treating those capabilities as selection criteria. And it means resourcing the diagnostic’s commercial launch alongside the drug’s, rather than assuming an approved test will find its own way into practice. Drug developers who take this seriously avoid the painful experience of launching a therapy that patients cannot access because nobody can get the test that identifies them.
A note on this snapshot
Diagnostics is a broad field and the companies named here are the most prominent rather than the only capable partners, with many specialized providers serving particular biomarkers, platforms, and geographies extremely well. What endures regardless of which partner you choose is the advice to engage early, prioritize demonstrated regulatory co-development experience, match the platform to your biomarker’s biology, and treat commercial access as seriously as approval, because a test that cannot reach clinical practice cannot find your patients.
Make it one program, not two
The organizing principle that prevents most companion diagnostic failures is to treat the drug and the test as a single program with a single timeline, single governance, and shared accountability, rather than as two projects that must eventually meet. When the diagnostic is owned by someone whose incentives and timelines are separate from the drug team’s, coordination fails at precisely the moments it matters most. Assign clear ownership of the combined program, plan both regulatory paths together, and hold one team accountable for both arriving on time, and the coordination problems that derail so many precision-medicine launches largely disappear.
The test must reach the clinic
It bears repeating because it is so often overlooked: an approved companion diagnostic that clinicians cannot easily order, laboratories do not run, and payers will not reimburse is functionally useless, no matter how rigorous its validation. Ask your prospective partner concretely how the test reaches ordinary clinical practice, which laboratory networks will offer it, and what the reimbursement pathway looks like. If they cannot answer clearly, that is a serious warning, because your drug’s commercial success depends on the answer as much as on your own launch execution.
For the full, maintained list of precision medicine and diagnostics companies, browse the BioMed Nexus precision medicine and diagnostics directory, and see our guides on choosing a companion diagnostics partner and precision versus personalized medicine.
Frequently asked questions
What are the leading companion diagnostics companies?
Roche, including Foundation Medicine, holds one of the largest franchises. Thermo Fisher and Agilent are major forces, Guardant Health leads in liquid biopsy, and Illumina, QIAGEN and Abbott are substantial participants. Myriad Genetics, NeoGenomics, Caris Life Sciences, Natera and Exact Sciences hold notable positions across genomic profiling and oncology testing.
What is a companion diagnostic?
A companion diagnostic is a test that identifies which patients are likely to benefit from a specific therapy, typically by detecting a biomarker such as a genetic mutation or protein expression. It is what makes precision medicine possible, because without the test you cannot reliably find the responders and the drug's benefit gets diluted across an unselected population.
How do I choose a companion diagnostics partner?
Prioritize regulatory track record in getting companion diagnostics approved alongside therapies, assess platform fit for your specific biomarker (tissue, sequencing or liquid biopsy), and weigh commercial reach and market access, since a test that is approved but not widely available cannot find your patients. Engage early, because a late diagnostic can delay a drug's launch.
