The professional's toolkit: quick calculations and sanity checks

Worked example:

• List price: $1,000 per unit
• Medicaid rebate: -$150
• Commercial PBM rebate: -$250
• Distribution fees: -$50
• Net price: $550

GTN discount = (1,000 − 550) / 1,000 = 45%

As of 2024-2025 estimates, industry-wide average GTN discounts in the US run 40-50% for branded drugs overall, and can exceed 70-80% for crowded categories like insulins or diabetes drugs (source: drugchannels.net, a widely cited independent industry blog). Always ask "list or net?" before reacting to a price headline.

Calculation 2: Market shareMarket shareThe percentage of total industry sales your company captures in a given period. It measures competitive position relative to rivals in a defined market.Voir la définition complète → from prescription data

Market shareMarket shareThe percentage of total industry sales your company captures in a given period. It measures competitive position relative to rivals in a defined market.Voir la définition complète → claims usually come from prescription-tracking data sold by firms like IQVIA (the dominant global health data and analytics provider). Two share metrics matter, and they tell different stories:

• TRx (total prescriptions): all prescriptions filled, new and refills. Reflects current usage.
• NRx (new prescriptions): only new prescriptions. Reflects momentum, an early signal of whether a drug is winning or losing versus competitors.

Worked example:

A drug has 40,000 TRx out of a category total of 500,000 TRx.

TRx share = 40,000 / 500,000 = 8%

If that same drug has 12,000 NRx out of 100,000 category NRx:

NRx share = 12%

NRx share above TRx share means the drug is *gaining* ground (it's grabbing new patients faster than its installed base implies). NRx below TRx signals decline. This is the single fastest way to check whether a "market leader" claim is backward-looking or genuinely accelerating.

Calculation 3: Peak sales estimate (the analyst's napkin math)

Peak sales is the maximum annual revenue a drug is expected to reachreachThe number of unique people exposed to your message in a given period. Unlike impressions, reach counts each person once, no matter how often they see it.Voir la définition complète → before generic or competitive erosion. The basic formula:

Peak sales = Eligible patient population × Diagnosis rate × Treatment rate × Drug's market share × Net price × Persistence rate

Worked example (illustrative, not a real drug):

• Eligible patients (US): 2,000,000
• Diagnosed: 60% → 1,200,000
• Treated: 50% → 600,000
• Drug's expected share of treated patients: 20% → 120,000
• Net annual price per patient: $15,000
• Persistence (patients still on therapy after 1 year): 80%

Peak sales = 120,000 × $15,000 × 0.80 = $1.44 billion

Compare that to the "$2 billion" claim from our opening. If a company's assumptions require, say, a 35% share or near-100% persistence to hit that number, you now know exactly which assumption to interrogate on the earnings call.

Calculation 4: Generic erosion curves

When a drug loses patent protection (or in Europe, when the SPC, supplementary protection certificate extending patent life, expires), generic competitors enter and prices collapse. This is governed in the US partly by the Hatch-Waxman Act, which grants the first generic filer 180 days of exclusivity.

Typical erosion patterns (US, small-molecule drugs, estimates):

• Volume share lost to generics: 70-90% within the first year
• Price erosion: 60-90% off branded net price within 12-24 months, especially once multiple generics enter

Europe tends to show slower volume erosion but steeper price cuts, driven by reference pricing systems where national payers cap prices based on the cheapest available generic.

Quick sanity check formula:

Remaining brand revenue (Year 2 post-LOE) ≈ Pre-LOE revenue × (1 − volume loss%) × (1 − price cut%)

Example: $1 billion pre-LOE (loss of exclusivity) revenue, 80% volume loss, 70% price cut:

$1B × 0.20 × 0.30 = $60 million remaining. That's a 94% total revenue collapse, consistent with what's typically observed for small-molecule brands facing multiple generic entrants.

Biologics behave differently: biosimilars (near-copies of biologic drugs, which cannot be exactly replicated like small-molecule generics) typically erode brand share more slowly, often 20-40% share loss in year one, because physicians and payers are more cautious about switching.

Calculation 5: The sanity-check ratio: R&D and margin benchmarks

Before trusting any pharma forecast, check it against sector-wide benchmarks (2024-2025 estimates, large-cap pharma):

• R&D as % of revenue: typically 15-20% for large research-based pharma companies (e.g., companies like Pfizer, Roche, Novartis, Merck)
• Gross margin: often 70-85% for branded pharma (reflecting low manufacturing cost relative to price), much lower (20-40%) for generics manufacturers
• Operating margin: roughly 25-35% for large-cap innovative pharma, lower for generics-heavy or diversified companies

If a company's P&L shows R&D at 5% of revenue while claiming a robust late-stage pipelinepipelineAll active sales opportunities across the stages of the sales process, together with their combined potential value and probability of closing.Voir la définition complète →, that's a red flag worth investigating. If a "generics" company reports 70% gross margins, check whether it actually has a branded or biosimilar portfolio driving that number.

For market-level context: the global pharmaceutical market was estimated at roughly $1.6-1.7 trillion in 2024 (source: IQVIA Institute reports), with the US representing close to 45-50% of global spending despite having about 4% of world population, a structural fact behind nearly every pricing and access debate in the sector.

🎬 [VIDEO: "How Drug Pricing Actually Works in the US" - youtube.com - search for recent explainers from Kaiser Family Foundation (KFF) or Marketplace on YouTube covering PBMs, rebates, and list vs. net pricing]

A one-page due-diligence checklist

When you see a pharma number in the wild, run it through this filter:

1. List or net? (applies to any price or revenue figure)

2. TRx or NRx? (applies to any share claim)

3. What assumptions drive the peak sales number? (population, share, price, persistence)

4. Small molecule or biologic? (determines expected erosion speed and pattern)

5. US or ex-US? (drivers, payers, and pricing mechanics differ sharply)

Key Takeaways

• Gross-to-net discounts average 40-50% in the US; never react to a US list price without asking about net price.
• NRx share rising faster than TRx share is the quickest tell that a product is winning, not just large.
• Peak sales = population × diagnosis × treatment × share × price × persistence; stress-test each input before trusting the headline number.
• Generic erosion typically wipes out 80-95% of small-molecule brand revenue within two years of patent expiry; biosimilars erode more slowly.
• Always benchmark against sector norms (R&D ~15-20% of revenue, gross margins 70-85% for branded pharma) before accepting any single company's numbers at face value.