CMC Challenges and Solutions in Botanical IND & NDA Development

The FDA approved its first botanical prescription drug in 2006. Nearly two decades later, only three more have followed. To many in the pharmaceutical industry, that number tells a story of failure — a pathway too difficult, too uncertain, and too risky to pursue. In a review article, we analyzed the challenges and solutions each approved botanical drug went through and summarized their successful approaches.

The Problem Is Not the Pathway

Botanical drugs are complex, multi-component preparations derived from plant materials. Unlike single-molecule drugs, they cannot be fully characterized at the molecular level. Their chemical profiles vary with cultivar, geography, harvest season, and processing conditions. By every measure of conventional pharmaceutical quality control, they are difficult products.

The FDA recognized this decades ago. Through two successive guidance documents in 2004 and 2016, and the establishment of a dedicated Botanical Review Team within the Center for Drug Evaluation and Research, the agency built a regulatory framework specifically designed for this complexity. At its core is a principle called the totality-of-evidence approach: rather than requiring the complete molecular certainty demanded of new chemical entity drugs, the FDA accepts aggregate evidence drawn from upstream raw material controls, chemical characterization, mechanistic bioassays, and multi-batch clinical data to assure product quality and therapeutic consistency.

The framework is sound. The four approvals prove it works. So why have so few botanical drugs made it through?

Lessons from Four Approved Drugs

Our review examines each of the four FDA-approved prescription botanical drugs — Veregen, Fulyzaq/Mytesi, NexoBrid, and Filsuvez — with a specific focus on the CMC challenges each program faced and the solutions that enabled approval.

• Veregen, a green tea catechin ointment for genital warts, could not achieve batch-to-batch consistency through conventional specifications because no correlation existed between individual catechin levels and clinical response. The solution was to restrict raw material to specific cultivars under Good Agricultural and Collection Practices, derive acceptance ranges from clinical trial batch data, and demonstrate through a dual-dose Phase 3 program that natural compositional variability did not affect clinical outcomes.

• Fulyzaq/Mytesi, an oligomeric proanthocyanidin for HIV-associated diarrhea, presented even greater characterization uncertainty — its oligomers could not be individually separated or quantified by any available analytical technique. The FDA required the development of a clinically relevant bioassay measuring chloride channel inhibitory activity as the primary quality specification, grounding quality assurance in what the drug does rather than what it contains.

• NexoBrid, a proteolytic enzyme concentrate from pineapple stems for burn debridement, took this a step further by electing the Biologics License Application pathway, where process-defines-product and functional activity assays are the established quality paradigm.

• Filsuvez, a birch bark triterpene gel for epidermolysis bullosa, leveraged orphan drug designation for commercial viability and quantitative triterpene fingerprinting as its quality anchor, supported by European clinical data demonstrating therapeutic consistency across the controlled compositional range.

Each program was different. Each product posed unique challenges. But five generalizable patterns emerge across all four: upstream raw material control as the quality foundation, characterization depth calibrated to product complexity, functional assays as compensatory evidence when chemistry alone is insufficient, clinical data as the ultimate quality anchor, and strategic regulatory pathway alignment as a CMC decision rather than merely an administrative one.

The Real Barrier: Predictability

If the framework works, why has uptake been so limited? Our review identifies several structural barriers.

1. The 10-to-15-year drug development timeline means that programs initiated under the mature 2016 Guidance are only now approaching the window for NDA submission. Most botanical drug sponsors are small companies whose development programs are interrupted by funding gaps, extending timelines further. Regulatory expertise specific to botanical drug INDs is scarce and largely resides outside the established contract research organizations that serve conventional pharmaceutical sponsors. And major pharmaceutical companies, despite evaluating the pathway, held back by short-term financial reporting pressures, institutional entrenchment in single-molecule thinking, lack of botanical science expertise, underdeveloped supply chains for pharmaceutical-grade botanical raw materials, and a perceived intellectual property disadvantage.

2. That last point deserves particular attention. The conventional view is that botanical drugs are harder to protect than single-molecule drugs because they lack composition-of-matter patents. Our review argues the opposite. The totality-of-evidence framework itself creates a multi-layered body of proprietary knowledge — specific raw material sources, specific manufacturing processes, specific analytical methods, specific bioassays, specific clinical datasets — that a generic competitor would need to independently reconstruct in its entirety. In practical terms, this barrier may exceed the protection of a single patent that can be designed around through molecular modification. The totality-of-evidence framework functions as a de facto intellectual property shield. It does not protect a molecule. It protects the entire integrated system that delivers the drug to patients.

The Gold Standard We Already Have

The central argument of our review is this: the totality-of-evidence principle, already articulated in the FDA Guidance and validated by four successful approvals, should serve as the gold standard for both regulators and sponsors.

• For sponsors, that means building development programs around the totality-of-evidence architecture from day one — investing in upstream raw material control during the IND phase, initiating bioassay development early when characterization limitations are foreseeable, and designing clinical programs that generate CMC-relevant data including multi-dose and multi-batch analyses.

• For the regulatory side, that means ensuring consistency across all disciplines of the IND review team. The Botanical Review Team possesses specialized expertise, but the complete review team includes clinical, nonclinical, and clinical pharmacology reviewers who may apply interpretive frameworks rooted in single-molecule expectations. When all reviewers apply the totality-of-evidence principle and calibrate CMC expectations to the appropriate IND stage, the process becomes predictable. When review comments default to conventional new chemical entity requirements for inherently complex botanical products, the resulting unpredictability discourages sponsors and reinforces the misperception that the pathway itself is flawed.

The Framework Exists. The Precedent Exists.

Four approved botanical drugs is not a story of failure. It is a proof of concept — for the regulatory framework, for the totality-of-evidence principle, and for the proposition that complex botanical products can meet modern FDA standards of quality, safety, and efficacy through a different but equally rigorous evidentiary architecture.

What is most needed now is alignment. Sponsors who build their programs on the principles the four approved drugs have demonstrated. Reviewers who apply the Guidance they helped create. When both sides of the table operate from the same framework, the botanical drug IND process becomes not only predictable but achievable — and more botanical drugs will reach the patients who need them.

he full article, "CMC Challenges and Solutions in Botanical Drug IND & NDA Development — Lessons Learned from Four Approved Botanical Drugs," is available in the Journal of Botanical Drugs. [https://botanicaldrugs.org/index.php/pub/article/view/7]