Protagonist Therapeutics, Inc. (PTGX): A Bull Case Theory

Wed, Sep 17, 2025, 11:45 AM 3 min read

We came across a bullish thesis on Protagonist Therapeutics, Inc. on BiotechBonanza’s Substack by AnotherBio. In this article, we will summarize the bulls’ thesis on PTGX. Protagonist Therapeutics, Inc.'s share was trading at $59.68 as of September 11th. PTGX’s trailing and forward P/E were 81.75 and 26.39 respectively according to Yahoo Finance.

Protagonist Therapeutics (PTGX) presents a compelling investment case following strong clinical progress and underappreciated fundamentals. The company, with a market cap of $3.6 billion and $615 million in net cash as of June 2025, is a hybrid royalty and development firm, giving it a unique risk/reward profile that challenges traditional valuation approaches. PTGX’s most valuable asset, Icotrokinra (Ico), an oral IL-23R peptide antagonist partnered with JNJ, is approaching FDA approval with robust Phase 2/3 data across multiple indications, including psoriasis, psoriatic arthritis, ulcerative colitis, and Crohn’s disease.

Its efficacy rivals or potentially surpasses injectables like Skyrizi and Tremfya, positioning it to capture significant market share in a $25 billion IL-23 class. PTGX stands to earn $400–$900 million in annual royalties, with upside from sales milestones and potential market expansion, making a base-case DCF value of $3–4 billion plausible.Rusfertide, partnered with Takeda, targets polycythemia vera with strong Phase 3 results, offering $100–$200 million in annual cash flow plus a $400 million opt-out payment, providing near-term value while preserving upside.

PTGX’s platform includes oral IL-17, oral hepcidin, and obesity drug candidates, offering high optionality and potential for significant future upside, particularly if early-stage clinical data impresses and attracts strategic interest. The balance sheet is strong, with minimal burn relative to upcoming catalysts, and management incentives are well-aligned with shareholder value.Multiple catalysts exist, including Ico approval, Rusfertide commercialization decisions, and pipeline readouts, while the market has yet to fully price in these assets.

The potential for strategic transactions, including royalty sales or platform acquisitions, could further unlock value. Overall, PTGX combines near-term cash flow, low-risk royalties, and high optionality from clinical assets, creating an asymmetric risk/reward profile for long-term investors willing to be patient in biotech.

Previously we covered a bullish thesis on Moderna, Inc. (MRNA) by YouAlwaysHaveAChoice in February 2025, which highlighted the company’s exposure to emerging viral threats, strong institutional positioning, technical bullish signals, and robust options activity supporting upside potential. The company's stock price has appreciated approximately by 100% since our coverage. The thesis still stands as MRNA’s optionality remains significant. AnotherBio shares a similar bullish view but emphasizes PTGX’s underappreciated clinical assets, royalties, and strategic optionality, providing a complementary perspective in biotech.