Financial due diligence checklist for a pharma investment or deal

Checklist item 1: IP litigation exposure

Most branded drug revenue depends on patent protection. Generic manufacturers routinely file challenges under the Hatch-Waxman Act (the US law governing generic drug approval and patent litigation, formally the Drug Price Competition and Patent Term Restoration Act of 1984).

What to check:

• Full list of Orange Book patents (the FDA's public list of patents tied to approved drugs, available at FDA Orange Book) covering the target's key products
• Any Paragraph IV certifications filed against those patents (a generic maker's formal notice that it intends to challenge patent validity)
• Pending litigation in US district courts and any settlement agreements with generic entrants, since "pay for delay" settlements draw antitrust scrutiny from the FTC (Federal Trade Commission)
• Patent cliff timing: when does composition-of-matter protection expire versus secondary patents (formulation, method of use) that are weaker and easier to challenge

Worked example: A target's flagship drug generates $400 million in annual revenue and its core patent expires in 2029, three years post-close. If a Paragraph IV challenge succeeds early, generic entry could cut that revenue by 80 to 90 percent within a year of launch (a commonly observed pattern for small-molecule genericization, treated here as an estimate since actual erosion varies by molecule and number of entrants). That risk alone can justify a material price adjustment or an earn-out structure instead of an all-cash deal.

Checklist item 2: Regulatory inspection history

The FDA and Europe's EMA (European Medicines Agency) inspect manufacturing sites, and a bad inspection can halt production overnight.

What to check:

• FDA Form 483 observations (formal notices of inspection findings) issued to the target's plants over the last five years, searchable via FDA's inspection database
• Any Warning Letters, which are more serious than 483s and signal unresolved compliance failures
• Consent decrees (court-enforced agreements that can restrict or halt manufacturing until remediation)
• EMA GMP (Good Manufacturing Practice) non-compliance reports for EU-facing sites
• Status of Corrective and Preventive Action (CAPA) plans: are they closed, or still open and unresolved

A single unresolved Warning Letter at a sole-source manufacturing site can freeze an entire product line. In 2023 to 2024, several generic and APIAPIApplication Programming Interface: a standardised interface that lets applications communicate and exchange data without knowing each other's internal workings.View full definition → (active pharmaceutical ingredient) manufacturers faced import alerts that cut off US supply, a reminder that manufacturing risk is financial risk, not just an operations footnote.

Checklist item 3: Rebate and chargeback accrualsaccrualsAccrual accounting records revenue and expenses when they are earned or incurred, not when cash changes hands, giving a more accurate picture of financial performance.View full definition →

This is the most technical and most commonly mis-modeled item in pharma financials.

In the US, list price is not what companies collect. Manufacturers pay rebates to PBMs (Pharmacy Benefit Managers) and health plans, chargebacks to wholesalers for sales at contracted lower prices, and Medicaid rebates mandated by federal law. Net revenue can be 40 to 60 percent below gross list price for many branded drugs (a widely cited range in pharma finance commentary, treated as an estimate since it varies significantly by product and payer mix).

What to check:

• Gross-to-net (GTN) bridge: the full walk from list price to net revenue, including rebates, chargebacks, discounts, and returns
• Accrual methodology: does the target book rebate liabilities based on actual claims data or rough estimates
• History of accrual true-ups or restatements (a red flag if liabilities were consistently under-accrued and then corrected in large one-time adjustments)
• Medicaid Drug Rebate Program obligations under Section 1927 of the Social Security Act
• Contract terms with major PBMs (CVS Caremark, Express Scripts, Optum Rx dominate the US market) and whether rebate rates step up over time

Simple worked calculation:

If a target books revenue near the gross figure and only later trues up the rebate accrual, EBITDAEBITDAEBITDA (Earnings Before Interest, Taxes, Depreciation, and Amortization) measures a company's operating profitability before financing and accounting decisions, used to compare core performance across firms.View full definition → (earnings before interest, tax, depreciation, amortization) in due diligence can look 20 to 30 percent higher than sustainable. Always ask for the quarterly GTN bridge for the last three years, not just the latest quarter.

Checklist item 4: Channel inventory stuffing

This is the Endo-style problem from the opening. Manufacturers sell to wholesalers (McKesson, Cencora, Cardinal Health dominate US distribution), and wholesalers can hold months of extra stock that has not actually reached patients.

What to check:

• Days of inventory on hand at major wholesalers, compared to historical norms (typically weeks, not months, for most therapeutic categories)
• Sell-through data (actual prescriptions filled, via IQVIA or similar data providers) versus sell-in data (shipments to wholesalers)
• Spikes in shipments in the quarters immediately before a sale process or fiscal year end
• Return reserves and whether they are adequate given inventory levels sitting in the channel
• Distribution agreements: do they include buy-back or return rights that create hidden liabilities

If sell-in consistently outpaces sell-through for several quarters, revenue growth is manufactured, not organic, and it will reverse as a revenue cliff after close.

Assembling the diligence workflow

A practical team sequences these checks rather than running them in parallel blind:

1. Legal and regulatory workstream: patent landscape, litigation docket, FDA/EMA inspection history

2. Financial workstream: GTN bridge reconstruction, accrual audit, channel inventory analysis using wholesaler and IQVIA data

3. Quality of earnings (QoE) report: an independent accountant's adjusted EBITDAEBITDAEBITDA (Earnings Before Interest, Taxes, Depreciation, and Amortization) measures a company's operating profitability before financing and accounting decisions, used to compare core performance across firms.View full definition → view that strips out one-time items and flags accrual risk

4. Red flag report synthesis: a short memo ranking the top five risks by dollar impact, not just by legal severity

Deal structures often respond directly to findings here: earn-outs tied to patent litigation outcomes, escrow holdbacks for regulatory remediation costs, and indemnification caps specifically carved out for rebate under-accrual.

🎬 [VIDEO: "How Pharma Companies Really Make Money (Gross to Net)" - youtube.com/results?search_query=pharma+gross+to+net+rebates - search this term for current explainer videos on how list price to net revenue works in US pharma pricing]

Key Takeaways

• Patent cliffs and Paragraph IV litigation can erase 80 percent or more of a drug's revenue within a year of generic entry; model this explicitly, don't treat patent expiry as a footnote.
• FDA Form 483s, Warning Letters, and consent decrees at manufacturing sites are financial risks, not just compliance issues, since they can halt supply overnight.
• The gross-to-net bridge is where pharma revenue quality lives or dies; always reconstruct it independently rather than trusting management's reported net revenue.
• Compare sell-in (shipments) to sell-through (actual prescriptions) to catch channel stuffing before it becomes a post-close revenue collapse.
• Structure the deal, not just the price, around these risks: earn-outs, escrows, and indemnification caps are the practical tools for pricing uncertainty you cannot fully resolve in diligence.