Small Populations. Enormous Stakes.
Regulatory strategy for orphan and ultra-rare programs — where the control arm is built from natural history and flexibility is the whole game.
You Will Never Run the Trial the Textbook Wants.
In a disease with a few hundred known patients, a large randomized controlled trial is not just impractical — it can be impossible, and sometimes unethical. The FDA knows this. Statute and guidance give the agency latitude to exercise scientific judgment on the quantity of evidence a rare-disease approval requires.
That flexibility is real. It is also earned. It rewards sponsors who engage early, characterize the disease rigorously, and design a study that answers the agency's question with the patients that exist. We translate flexibility into a defensible development plan — through the OOPD, CBER's and CDER's rare-disease programs, and the START and RDEA pilots.
Most rare diseases trace to a single defined mutation — which sharpens the science and raises the stakes on getting the trial design right the first time.
The Designations Are a Stack. Assemble Them in the Right Order.
Orphan development is not one designation — it is a sequence of incentives and expedited programs, each requested at the moment it does the most work. Stacked deliberately, they de-risk the economics and compress the timeline at once.
Orphan Drug Designation
For diseases under 200,000 US patients: seven years of market exclusivity, tax credits on clinical costs, and a waiver of the user fee. The foundation the rest of the stack builds on.
Rare Pediatric Disease Designation
For serious, life-threatening rare diseases in children — and, when the program is authorized, a priority review voucher on approval that carries real transferable value.
Fast Track & Breakthrough Therapy
Rolling review and intensive FDA guidance where preliminary evidence is strong — the engagement that makes a small, unconventional trial credible to the review division.
START & RDEA Pilots
Milestone-based FDA feedback (START) and structured support for developing and validating novel rare-disease endpoints (RDEA) — the newest tools for the hardest programs.
Accelerated Approval
Approval on a surrogate reasonably likely to predict benefit — often the only feasible path in a slowly progressive rare disease — paired with a confirmatory commitment.
In rare disease, the comparator arm is an asset you build — a rigorously collected picture of the untreated course of the disease.
The Natural History Study Is the Backbone of the Whole Program.
When you cannot randomize, the untreated course of the disease becomes your comparator. A well-designed natural history study anchors the external control, surfaces the endpoints that actually move, and defines the patient population the FDA will recognize.
Done late or loosely, it sinks the program — mismatched patients, endpoints that don't discriminate, data the agency won't accept as a control. We build natural history and external-control strategy the way reviewers evaluate it: prospectively, with the estimand and the comparison defined before the pivotal trial enrolls.
When You Can't Run a Classic RCT, You Design Around It.
Rare-disease pivotal trials borrow from a specialized toolkit. Choosing the right design — and defending it to the division before you start — is the difference between an approvable dataset and an uninterpretable one.
Single-Arm + External Control
Every patient receives the therapy; the natural history cohort supplies the control. The workhorse design when withholding treatment is not an option.
Crossover & N-of-1
Each patient acts as their own control across treatment periods — powerful when the disease is stable and the effect is reversible, common in ultra-rare programs.
Bayesian & Adaptive
Designs that borrow strength from prior and external data and adapt as small numbers accrue — pre-specified and pre-agreed so the analysis holds up at review.
Basket & Platform
One protocol spanning multiple mutations or sub-populations that share a mechanism — efficient when the biology, not the diagnosis, defines eligibility.
Fit-for-Purpose Endpoints
When no validated outcome measure exists, you develop one — a clinical outcome assessment built with patients through the RDEA pilot and PFDD.
Patient-Focused Development
Advocacy organizations and patients shaping the endpoints, the meaningful change, and the benefit–risk — evidence the FDA increasingly expects to see.
In Rare Disease, the Community Is at the Table — So Bring Them Early.
Rare-disease families often know the natural course of their condition better than the literature does. Patient-Focused Drug Development turns that knowledge into regulatory evidence — defining which outcomes matter, what magnitude of change is meaningful, and how much risk the community will accept for benefit.
We help sponsors partner with advocacy organizations credibly and compliantly — so the patient voice strengthens the endpoint strategy and the benefit–risk case, rather than arriving as an afterthought at the advisory committee.
The people who live the disease help define what a meaningful treatment effect actually is.
The Flexibility Is Real. So Is the Scrutiny.
Regulatory flexibility rewards rigor, not thin evidence. The programs that struggle are the ones that mistook "smaller trial" for "lower bar." A single, well-characterized, well-defended dataset carries a rare-disease approval — a loose one does not.
US patients defines an orphan indication — but the ultra-rare programs of a few hundred patients are where the design creativity truly begins.
adequate and well-controlled study can support approval in rare disease when the evidence is compelling — the flexibility the statute permits, applied case by case.
and often is the only way to run it. The sponsors who succeed engage the OOPD and the review division years before the pivotal trial.
Six Failure Modes We Are Brought In to Prevent.
In small populations there is no second cohort to fix a design mistake. Getting it right the first time is the entire discipline.
A natural history study built too late
Starting the pivotal trial without a prospective, rigorously matched external control the agency will accept — the most common reason rare-disease datasets become uninterpretable.
An endpoint that doesn't discriminate
Relying on an outcome measure never validated in the disease, so a real treatment effect cannot be distinguished from noise in a small sample.
Designation strategy left on the table
Missing Orphan, Rare Pediatric, or Breakthrough designations — or requesting them out of sequence — and forfeiting exclusivity, vouchers, or FDA engagement.
Engaging the FDA too late
Skipping the START and RDEA pathways and pre-submission meetings, then discovering at filing that the division never agreed to the unconventional design.
CMC scaled for a blockbuster
A control strategy and comparability plan that ignores tiny batch sizes, a single manufacturing site, and the realities of an ultra-rare supply chain.
The patient community brought in last
Treating advocacy engagement as PR rather than evidence, and losing the benefit–risk argument the community could have carried.
Rare-Disease Regulatory Leadership That Has Done It With the Patients Who Exist.
Our rare-disease leads have designed natural history studies, negotiated external-control acceptability, stacked orphan incentives, and taken ultra-rare programs through accelerated approval.
"In a disease with two hundred patients, you don't get a do-over. The plan has to be right — the natural history, the endpoint, the designations, the FDA agreement — before the first patient enrolls."
The discipline we bring to every orphan and ultra-rare program, from designation through approval.
Developing for a Rare Disease? Design the Evidence Before the Patients Run Out.
Bring senior rare-disease regulatory leadership in early — while the natural history, endpoints, and designation strategy are still yours to shape.
Senior-led. Embedded in your team. No junior hand-offs.