Infectious Disease Deals Are Shifting to Milestone-Heavy Structures

The Upfront Is Shrinking — Relatively Speaking

Across biopharma deal-making, infectious disease has always been the awkward middle child. Not as flashy as oncology. Not as structurally straightforward as rare disease. But the deals keep happening, and they've been quietly evolving in a direction that every ID-focused biotech founder needs to understand before entering a process.

The trend is clear: infectious disease licensing transactions are becoming more milestone-heavy relative to their total deal values. Upfront payments as a share of headline numbers have compressed, while the pools of development, regulatory, and commercial milestones have expanded. This isn't just a post-pandemic correction. It reflects how pharma acquirers are pricing risk in a therapeutic area defined by binary clinical outcomes, unpredictable market dynamics, and persistent reimbursement headwinds.

Why ID Gets Treated Differently

The structural logic is straightforward once you understand how pharma BD teams model infectious disease assets.

Oncology deals can lean on large, growing patient populations and pricing power. Rare disease transactions benefit from clear regulatory pathways and orphan drug exclusivity. Infectious disease sits in a harder spot. Antibiotic stewardship limits volumes. Pull incentive programs like the PASTEUR Act remain stalled in various legislative forms. Antiviral markets can spike and collapse — ask anyone who built a commercial model around COVID-19 antivirals in 2021 and watched the addressable market shrink by 80% in two years.

So acquirers hedge. They structure deals with lower upfronts and attach value to milestones that derisk the specific uncertainties of ID programs: Phase 3 enrollment completion, FDA approval, first commercial sale, and increasingly, revenue-based milestones tied to annual net sales thresholds.

The Pfizer/Seagen deal — while oncology-focused — set a structural precedent for how large pharma thinks about paying for pipeline optionality. In infectious disease, the same instinct plays out through licensing structures rather than outright acquisitions. Pharma wants the option to scale into ID assets without committing billions upfront to a market that may or may not materialize.

The Milestone Architecture Has Gotten More Sophisticated

It's not just that milestones are bigger. They're more granular. Deals we track show an increasing tendency to break development milestones into narrower gates: IND acceptance, first patient dosed, enrollment completion, database lock, filing acceptance, and approval — each with its own payment. Five years ago, a typical ID deal might have had two or three development milestones. Now it's common to see five or six, sometimes more.

This granularity works in both directions. For the licensor, it creates more frequent cash infusions that can fund operations between gates. For the licensee, it limits exposure at each decision point. The total milestone pool might look impressive in a press release, but the probability-weighted value is meaningfully discounted.

Commercial milestones have also shifted. Rather than simple revenue thresholds ($500M, $1B in annual net sales), deals increasingly include tiered royalty adjustments and sales-based milestones that ratchet upward. This is pharma's way of saying: we'll pay more, but only if the market actually develops.

For antifungal and novel antibiotic programs, where the commercial trajectory is genuinely uncertain, these structures dominate. The AbbVie/Paratek and GSK/Spero deals from prior years illustrate how established pharma partners approach anti-infective assets — carefully, with contingent value spread across a long timeline.

Upfront Benchmarks and What to Expect

Without citing specific aggregate figures from our database as it refreshes, the qualitative pattern is instructive. Infectious disease upfronts for preclinical and Phase 1 assets tend to cluster well below those in oncology for comparable stages. Phase 2 assets command more attention, but even there, the upfront-to-total-deal-value ratio in ID lags behind therapeutic areas with clearer commercial visibility.

What does this mean in practice? A Phase 2-ready anti-infective program with differentiated mechanism of action and a clear regulatory path might expect an upfront in the low tens of millions, with total deal value reaching into the hundreds of millions via milestones. Compare that to a Phase 2 oncology asset with biomarker-selected patient populations, where upfronts routinely exceed $100M.

These benchmarks are available in real-time on Solidus, our deal terms platform.

The gap isn't about asset quality. It's about market risk. And it means ID-focused biotechs need to run their processes differently.

Pandemic-Era Distortions Are Fading

The 2020-2022 period was an anomaly. Antiviral and vaccine deals commanded enormous upfronts and total values driven by acute demand and government-backed procurement. Those days are over. The Merck/Ridgeback Biotherapeutics deal for molnupiravir, with its blockbuster revenue trajectory, was a product of extraordinary circumstances that are not repeatable in normalized markets.

What remains is a return to pre-pandemic structural norms — but with one important difference. Pharma's appetite for anti-infective assets hasn't disappeared. AMR (antimicrobial resistance) remains a first-order public health concern, and pipeline gaps in novel antibiotics are well-documented. The WHO's priority pathogen list continues to expand. But the commercial infrastructure to monetize these assets hasn't caught up, which keeps deal structures tilted toward contingent payments.

Pandemic-preparedness platforms — broad-spectrum antivirals, next-generation mRNA-based approaches — still attract interest, but the structure of those deals looks more like traditional platform deals with option payments and program-specific milestones than the massive upfront commitments of the COVID era.

Implications

If you're running an infectious disease company and preparing for a licensing process in the next 12-18 months, here's what matters.

First, don't anchor your board on headline deal value. The ratio of upfront to total consideration is going to be lower in ID than in other therapeutic areas, and that's structural, not a reflection of your asset's quality. Frame internal expectations around the upfront payment and the probability-weighted value of near-term milestones. A $30M upfront with $400M in milestones is a different proposition than a $100M upfront with $200M in milestones, and your cash runway planning should reflect the actual payment timing.

Second, negotiate milestone granularity to your advantage. More milestone gates mean more cash events, but they also mean more decision points where a partner could walk away. Push for milestones tied to events you control (IND filing, first patient dosed) rather than events the partner controls (commercial launch timing, formulary access). The distinction matters enormously for your financial planning and your leverage in the partnership.

Third, understand that royalty rates in ID deals tend to be competitive — often in the low-to-mid teens for differentiated assets — because pharma knows the upfront is modest and the milestones are contingent. If you're accepting a lower upfront, make sure the royalty economics compensate. Tiered royalties with meaningful floors protect you if the partner under-invests in commercialization.

Finally, if you're an investor evaluating ID-stage companies, pay close attention to the deal structure assumptions embedded in management projections. A company modeling $200M upfronts for preclinical anti-infective assets is disconnected from market reality. The capital-efficient play in ID is a company that can reach a Phase 2 data readout on $50-80M in total funding and command a partnership that covers remaining development costs through milestones — not one that needs a massive upfront to return the fund.