Almost every biotech licensing announcement ends with a phrase that gets skimmed past: the licensor is "eligible to receive tiered royalties on global net sales of marketed products." That clause is the third and most contingent economic layer of a deal — after the upfront payment and the milestone "biobucks" — and the word tiered is doing specific work. Understanding it means understanding that the royalty rate in a modern license is rarely a single flat number; it is a schedule that changes with sales volume and with the legal life of the product's protection.

Start with the base concept. A royalty is a percentage of a product's net sales — gross sales less defined deductions such as rebates, discounts, returns, and certain distribution costs — paid by the licensee (the partner that commercializes the drug) to the licensor (the company that out-licensed the asset). "Net," not gross, is the contractual base, which is why the effective dollars are always lower than a naive percentage of headline revenue suggests. A real, SEC-filed collaboration states the royalty layer in exactly this form.

"Septerna is also eligible to receive tiered royalties on global net sales of marketed products. Novo Nordisk will cover all R&D expenses for partnered programs under the collaboration. In addition, Septerna has the right to opt-in to a worldwide profit-share for one program, in lieu of future milestones and royalties for that product candidate."— Septerna, Inc., Form 8-K Exhibit 99.1 (filed with the SEC), source

Two structural points sit inside that disclosure. First, "tiered" tells you the rate is a schedule, not a scalar — and the directionality is the next thing to pin down. Second, the same sentence shows that royalties are optional alternatives in some structures: the licensor can "opt-in to a worldwide profit-share for one program, in lieu of future milestones and royalties," meaning the parties built a switch between a royalty economic model and a profit-share model. That is a reminder that the royalty is one configurable layer among several, not a fixed feature.

Step-ups versus step-downs

Tiering runs in two directions, and the difference matters. A step-up (or ascending) royalty raises the percentage as cumulative or annual net sales cross higher thresholds — for example, a lower rate on the first band of annual net sales, a higher rate on the next band, and a higher rate again above a top threshold. Step-ups reward commercial success: the licensor's take per dollar grows as the product scales, aligning the licensor with blockbuster outcomes.

A step-down (or descending) royalty reduces the rate when a defined condition occurs. The most common triggers are tied to the erosion of exclusivity: loss of patent protection in a territory, entry of a generic or biosimilar above a market-share threshold, or the expiration of a contractually defined royalty term (often expressed as the longer of a patent-life period or a fixed number of years from first commercial sale). When one of these fires, the royalty rate drops — sometimes to a reduced "know-how" rate, sometimes to zero. Step-downs exist because the value the licensee receives falls once the asset is no longer protected: paying a full innovator royalty on a product facing generic competition would overpay for protection that no longer exists. The step-down clause writes that adjustment into the contract in advance.

The two mechanisms frequently coexist in a single agreement: a step-up schedule across sales bands while exclusivity holds, plus step-down provisions that cut the rate once patents lapse or competitors enter. The net effect is a royalty that rises with commercial success and falls with the loss of legal protection — a curve, not a line.

How royalties are disclosed and how to read them

Like the rest of a license's economics, the royalty structure is summarized in the deal's 8-K and detailed in the license agreement filed as an exhibit on sec.gov. Specific royalty percentages are frequently redacted as confidential commercial information under the SEC's rules, so a public reader often sees "tiered royalties" without the exact bands — but the agreement still discloses the existence and mechanics of the tiering, the net-sales definition, the royalty term, and the step-down triggers, even where the numbers themselves are withheld. The reportable facts are therefore the structure and the conditions, not always the rate.

One more mechanism frequently sits alongside the tiers and deserves attention: royalty stacking and the offset provisions that respond to it. When a marketed product is covered by intellectual property licensed from more than one party, the commercializing partner can owe royalties to several licensors at once — royalties "stacked" on the same sales. License agreements commonly address this with stacking-deduction clauses that let the payor reduce the royalty owed to one licensor by some portion of third-party royalties it must pay on the same product, often subject to a floor below which the rate cannot fall. Related provisions reduce royalties when there is no valid patent claim covering the product in a given country (a "no-patent" or know-how rate) or when generic competition reaches a defined market-share threshold. Each of these is, in effect, another conditional adjustment to the headline rate, and each is the kind of term that is spelled out in the agreement even when the base percentages themselves are redacted.

The discipline for reading a royalty line follows from its place in the stack. Royalties are the last and most conditional layer: they pay only if a product is approved and sold, they accrue on net sales, their rate moves by tier, and they can step down or terminate on loss of exclusivity. A company "eligible to receive tiered royalties" has a contingent claim on a future revenue stream that does not yet exist, governed by a schedule whose shape — step-up on success, step-down on competition — is defined in the agreement. The headline deal value folds the best-case royalties into its "up to" figure; the filing on sec.gov is where the actual rules of the royalty are written down.