Introduction
Companion diagnostics sit in an unusual regulatory position: a diagnostic test that is developed and reviewed alongside a drug, with its own regulatory pathway that is deliberately linked to the drug's approval. A companion diagnostic tells a clinician whether a specific patient is likely to respond to a specific therapy, and increasingly that test is co-developed and co-reviewed with the drug it pairs with. For regulatory affairs professionals, this has quietly created a specialty that draws on both pharmaceutical and medical device regulatory knowledge, and the people who can move fluently between the two frameworks are in real demand.
This piece looks at why companion diagnostics have become their own hiring niche, what the work actually involves, and how job seekers with either a device or a drug regulatory background can position themselves for it.
Why companion diagnostics don't fit neatly into either track
A conventional regulatory affairs career in life sciences tends to split fairly early between drug/biologic regulatory work and medical device regulatory work. The frameworks are genuinely different: drugs and biologics move through NDA, BLA, or MAA pathways with an emphasis on clinical safety and efficacy data; devices move through 510(k), De Novo, or PMA pathways (in the US) or through MDR/IVDR conformity assessment (in the EU), with a different emphasis on analytical and clinical validation of the device itself.
Companion diagnostics require both. In the US, FDA typically expects companion diagnostics tied to certain drug approvals to be reviewed through the PMA pathway for in vitro diagnostics, submitted in a way that is coordinated with the therapeutic product's own application, often resulting in simultaneous approval. The regulatory professional working on this program has to understand the therapeutic product's clinical development plan and the diagnostic's analytical and clinical validation requirements, and has to manage two review timelines that are explicitly meant to converge.
What the work actually looks like
Regulatory professionals in this space spend a meaningful amount of time on cross-functional coordination between the therapeutic sponsor and the diagnostic developer, which are frequently different companies working under a co-development agreement. That adds a layer of contractual and communication complexity on top of the technical regulatory work: agreeing on data sharing, aligning on submission timing, and making sure the labeling for the drug and the labeling for the diagnostic are consistent with each other.
On the technical side, the role involves working with analytical validation data (does the test accurately and reproducibly detect the biomarker it's designed to detect) and clinical validation data (does the biomarker status the test identifies actually correlate with the clinical outcome the drug label is claiming). Regulatory professionals need enough fluency in both bodies of evidence to identify gaps early, well before a submission is anywhere near ready.
Where the hiring demand is coming from
The growth in targeted and precision therapies — oncology treatments tied to specific genetic mutations, and a broadening set of therapies in other areas relying on biomarker-driven patient selection — has steadily increased the number of programs that need a companion diagnostic. Every one of those programs needs regulatory affairs professionals who can operate across the drug and device frameworks, and there simply aren't that many people who have built that dual fluency.
This shows up in hiring in a few recognizable ways: diagnostic companies posting roles that explicitly ask for familiarity with drug development timelines and FDA's expectations for co-development, pharmaceutical companies with precision medicine portfolios building out small internal teams focused specifically on diagnostic partnerships, and specialized CROs and consultancies building companion diagnostics practices to serve both sides of these partnerships.
The organizations most active in this hiring
Large diagnostic manufacturers with established oncology and precision medicine franchises are consistent hirers into companion diagnostics regulatory roles, since they typically run multiple co-development partnerships in parallel and need dedicated regulatory staff who understand the partnership structure as well as the science. Large pharmaceutical companies with oncology or other biomarker-driven portfolios increasingly build small internal teams focused specifically on liaising with diagnostic partners, rather than routing that work through a generalist regulatory affairs group.
Beyond the largest players, a growing number of specialized CROs and regulatory consultancies have built dedicated companion diagnostics practices, recognizing that many mid-size biotech and diagnostic companies don't have the internal headcount to justify a full-time specialist but still need that expertise for a specific program. These consultancies can be a useful entry point for regulatory professionals who want exposure to multiple companion diagnostics programs across different therapeutic areas relatively quickly, compared to waiting for that experience to accumulate within a single company's pipeline.
How to position yourself for these roles
If your background is in medical device or IVD regulatory affairs, the fastest way to become relevant to companion diagnostics hiring managers is to build familiarity with drug development timelines, clinical trial phases, and how a therapeutic sponsor's regulatory strategy interacts with a diagnostic submission. Reading FDA guidance specifically addressing in vitro companion diagnostic devices, and following how recent approvals have paired drug and diagnostic labeling, is a reasonable starting point that doesn't require a formal credential.
If your background is in pharmaceutical or biologics regulatory affairs, the reverse applies: build familiarity with IVD-specific regulatory concepts like analytical sensitivity and specificity, clinical validation study design for diagnostics, and the PMA pathway structure. Some professionals also pursue targeted continuing education through RAPS or similar organizations that address diagnostics-specific regulatory content.
In either direction, the credibility marker that hiring managers look for isn't a certification — it's evidence that you've actually worked a program that required you to operate across both frameworks, even if only as one contributor on a larger team. If you haven't had that opportunity yet, volunteering for or seeking out a cross-functional liaison role on a precision medicine program at your current company is often the most practical way to get that experience before making an external move.
The compensation and career trajectory picture
Because the pool of professionals with genuine dual fluency is smaller than the pool of drug-only or device-only regulatory professionals, companion diagnostics specialists are often positioned as valuable hires rather than commodity roles, and the work tends to sit at mid-to-senior levels rather than entry-level, since it requires enough foundational regulatory experience in at least one track to build on. It's a reasonable specialty to aim for if you want work that stays technically interesting and cross-functionally complex rather than becoming repetitive.
Career trajectories from this niche tend to lead toward regulatory leadership roles in precision medicine-focused organizations, or toward consulting, where the ability to translate between drug and device regulatory frameworks for clients is a genuinely scarce and valuable skill.
What makes co-development timelines genuinely difficult
The core scheduling challenge in a companion diagnostics program is that the two development timelines rarely move at the same pace naturally, and someone has to actively manage them into alignment. A therapeutic's clinical trial timeline is driven by patient enrollment, safety monitoring, and efficacy readouts that can shift by months. The diagnostic's analytical validation work has its own dependencies — reagent availability, assay optimization, cross-site reproducibility testing — that don't automatically track the drug's timeline.
When the two sides are run by separate companies under a co-development agreement, the regulatory function often becomes the primary point of coordination, translating between the diagnostic developer's technical milestones and the therapeutic sponsor's clinical and regulatory milestones. This requires a degree of comfort with ambiguity and cross-company diplomacy that's less common in a single-company regulatory role, where at least everyone reports up through the same organization.
Retrospective diagnostic development — validating a test against biomarker data collected earlier in a therapeutic's clinical program rather than developing the test in parallel from the start — is another pattern regulatory professionals in this space need to understand, since it comes with its own evidentiary expectations and is treated differently by regulators than a test co-developed from the outset.
Where these programs commonly run into trouble
A recurring failure pattern is starting diagnostic development too late relative to the therapeutic program, so the diagnostic becomes the critical path item holding up an otherwise-ready drug submission. Regulatory professionals who've worked these programs tend to emphasize early engagement — getting the diagnostic partner identified and analytical validation work underway well before the therapeutic's pivotal trial is complete, not after.
Labeling misalignment is another common issue: the drug label and the diagnostic's instructions for use need to describe the same patient population and the same biomarker cutoff in consistent terms, and inconsistencies that seem minor internally can become a substantive question during health authority review. Part of the regulatory function's job on these programs is catching that kind of misalignment well before submission, which requires someone who's genuinely reading both documents side by side rather than assuming each workstream is handling its own piece correctly.
Conclusion
Companion diagnostics regulatory work isn't a large hiring category in absolute terms, but it's a growing one, and it rewards exactly the kind of professional who's willing to build fluency outside their original track. If you're a device-side or drug-side regulatory professional looking for a way to differentiate yourself and you have genuine interest in precision medicine, deliberately building companion diagnostics knowledge is one of the more durable ways to do it.