The Problem with Both Mistakes
Under-supply stops a clinical trial. Patients cannot be dosed, sites go on hold, and the timeline slips in ways that are expensive and sometimes impossible to recover. The consequences are obvious and everyone works hard to avoid them.
Over-manufacturing is less dramatic but equally costly. A 10 kilogram GMP batch of an HPAPI drug product that was never used represents not just the direct manufacturing cost, but the slot on the manufacturing schedule, the stability testing, the storage fees, and the disposal costs when it expires. For complex or expensive drug products, over-manufactured material that is destroyed at expiry can represent a significant proportion of the total clinical development budget.
The goal of clinical supply planning is not to avoid one of these outcomes. It is to navigate intelligently between both of them.
The Variables That Make Clinical Supply Hard to Plan
Enrolment Uncertainty
Clinical trial enrolment is notoriously hard to predict. Sponsors routinely underestimate the time needed to identify eligible patients, obtain consent, and complete screening. An enrolment model that assumes 100% of sites are active from month one, and that each site enrols patients at the projected rate, is an optimistic model that will almost always overestimate how quickly supply is consumed.
Protocol Amendments
Protocol amendments change the treatment duration, the dosing regimen, or the patient population. Each amendment is a supply planning event. An amendment that extends the treatment period from 12 weeks to 24 weeks doubles the supply requirement per patient. An amendment that adds a new cohort requires material that may not have been manufactured yet.
Drug Wastage
Unused drug at each clinical site, partially used kits, returned doses, and material destroyed due to temperature excursions all represent supply losses that must be planned for. Wastage rates vary by dosage form, route of administration, and site logistics, but assuming zero wastage is unrealistic.
The Statistical Approach: Probability of Sufficient Supply
Rather than planning to a single expected scenario, best-practice clinical supply planning uses simulation to generate a probability distribution of supply outcomes. Monte Carlo simulation, using distributions for enrolment rate, dropout rate, and wastage rather than point estimates, gives the supply planner a risk profile rather than a single number.
The output is a probability of sufficient supply (PoSS) at each potential manufacturing quantity. The sponsor then makes an informed decision about the trade-off between manufacturing more (higher PoSS, higher cost) and manufacturing less (lower cost, higher risk of supply shortage). For a Phase III pivotal trial, a PoSS of 95% might be acceptable. For an exploratory Phase I study, a lower threshold might be appropriate given the higher likelihood of protocol change.
Supply Planning Approaches by Trial Phase
| Trial Phase | Typical Supply Strategy | Key Planning Assumptions |
| Phase I SAD/MAD | Single manufacturing campaign covering all cohorts plus safety margin; conservative overage | Small patient numbers; tight dose range; cohort-by-cohort release allows staged manufacture if needed |
| Phase I/II first-in-class | Two campaigns: initial supply for early cohorts; second campaign triggered by interim data | High uncertainty in enrolment and dose selection; adaptive manufacture preferred over single large campaign |
| Phase II proof-of-concept | Statistical supply model; manufacture to defined PoSS; rolling resupply trigger defined | Enrolment modelling using investigator projections; monthly supply review meetings |
| Phase III global | Full Monte Carlo simulation; regional depot strategy; safety stock at each depot | Site-level enrolment projections; wastage rates from Phase II; country-specific import lead times |
| Adaptive design trials | Supply model updated at each interim analysis; flexible manufacturing agreements with CDMO | Scenario planning for each adaptive arm; close coordination between statistical and supply planning teams |
The Packaging and Labelling Layer
Supply planning is not just about how much drug to manufacture. It is also about how to package it. A single GMP bulk batch can be held and packaged into country-specific labelled kits as the trial progresses, allowing the labelling to be adapted to the actual trial countries without over-commitment to a specific national market early in the programme.
This just-in-time packaging approach requires a CDMO with clinical packaging capability and a project management model that coordinates the packaging schedule with the enrolment forecast. The alternative, packaging everything upfront for all anticipated markets, results in large amounts of labelled material that may expire before it is used if enrolment in specific markets is slower than projected.
How Ardena Supports Clinical Supply Planning
Ardena’s clinical supply team at Assen works with sponsors to develop supply models, design packaging strategies, and manage the coordination between GMP manufacturing, clinical packaging, and global distribution. The team has experience across Phase I through Phase III programmes and can support both simple fixed-supply and complex adaptive supply strategies.
