Episode 69: Summit Therapeutics

In this episode of Petri Dish Perspectives, we explore the remarkable rise of Summit Therapeutics, a biotech that transformed itself from an infectious-disease company into one of the most closely watched oncology companies in the world. At the center of the story is ivonescimab, a next-generation bispecific antibody targeting both PD-1 and VEGF and a drug that could potentially challenge Merck’s blockbuster Keytruda.

We’ll dive into Summit’s origins, the company’s dramatic pivot, the story behind its partnership with China’s Akeso, and the science behind why combining immune checkpoint inhibition with VEGF blockade could create a powerful new approach to cancer treatment. We’ll also break down the clinical data in lung cancer, Summit’s growing pipeline, the massive commercial opportunity, and the risks surrounding regulatory approval, clinical durability, and the company’s heavy dependence on a single lead asset.

But Summit’s story goes far beyond one cancer drug. Ivonescimab represents a broader shift in how medicines are discovered and commercialized, with innovative assets increasingly emerging from Chinese biotech and being licensed by Western companies for global development. Could Summit become the company that brings a new generation of cancer therapeutics to the world and could ivonescimab really become a challenger to Keytruda?

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Transcript

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Hello and welcome to Petri Dish Perspectives, the podcast where we geek out about science and the companies shaping the future of healthcare. I'm your host, Manead, and I'm a PhD scientist by training, storyteller by choice. With every new episode released on Thursday, my goal is to deliver digestible pieces of information on healthcare companies under 30 mins.

And the reason investors and pharmaceutical companies are paying attention is simple: ivonescimab has produced clinical data suggesting that it could potentially challenge the dominance of Keytruda, Merck's blockbuster PD-1 inhibitor and one of the biggest-selling drugs in pharmaceutical history. In a Phase 3 study in China, ivonescimab plus chemotherapy reduced the risk of death by 34% compared with tislelizumab plus chemotherapy in previously untreated advanced squamous non-small cell lung cancer. That result was presented in the plenary session at ASCO 2026, making it one of the most closely watched oncology datasets of the year. And notably, this marks the first time a China-originated investigational oncology drug has been selected for the ASCO plenary session in the society's 61-year history — a milestone worth pausing on.

But there is a major twist to this story. The drug was discovered in China, the company developing it in China is Akeso, and Summit essentially acquired the Western rights. That makes this not just a story about a promising cancer drug. It's a story about the changing geography of pharmaceutical innovation, the rise of Chinese biotech, the economics of licensing, the future of bispecific antibodies, and whether data generated in China can translate into a successful U.S. drug approval.

And as of August 2026, Summit is awaiting an FDA decision on its application in EGFR-mutated non-small cell lung cancer, with a PDUFA goal date of November 14, 2026. Meanwhile, questions about regional consistency in the global HARMONi trial have kept analysts cautious even as the ASCO data impressed.

So today we're going to unpack how Summit went from an antibiotic company to one of biotech's biggest oncology bets, what exactly makes ivonescimab different, why Merck is the company everyone is watching, and whether Summit actually has what it takes to turn this scientific bet into a blockbuster.

Quick disclaimer, I give full credit to the original articles cited in the references in the transcript!

Grab a coffee or tea, settle in, and let’s jump in!

2. Before Ivonescimab: The Summit That Almost Nobody Was Watching

To understand Summit, you actually have to start with a completely different company. Before ivonescimab, Summit was focused on infectious disease. Its lead asset was ridinilazole, an experimental antibiotic designed to treat Clostridioides difficile infection while preserving the gut microbiome. The concept was actually quite interesting: traditional antibiotics can disrupt the microbiome, potentially contributing to recurrent C. difficile infections, whereas ridinilazole was designed to selectively target C. difficile while preserving more of the surrounding microbiome. Earlier clinical data showed numerical differences favoring ridinilazole over vancomycin on recurrence and microbiome preservation.

But the problem was that promising science does not automatically translate into an approvable drug. The Phase 3 Ri-CoDIFy program showed ridinilazole resulted in a higher observed sustained clinical response rate than vancomycin but did not meet the study's primary endpoint for superiority. And in September 2022, the company announced it would seek a partner or divestiture for ridinilazole and discontinue its remaining active study.

And this is where the Summit story gets fascinating. The company essentially needed a new future.

At the same time, on the other side of the world, Akeso was developing an entirely different kind of drug. Akeso, founded and led by Michelle Xia, had developed ivonescimab, an antibody designed to combine PD-1 blockade with VEGF inhibition. Summit entered into a license agreement with Akeso on December 5, 2022, paying a $500 million upfront payment for rights to develop and commercialize ivonescimab in the United States, Canada, Europe, and Japan, with a total potential deal value of up to $5 billion including regulatory and commercial milestones, plus low double-digit royalties on net sales.

Think about how dramatic that pivot was. Summit went from a struggling infectious-disease biotech with a stalled lead program to a company with rights to a potentially transformative oncology asset.

And that is where Bob Duggan becomes central to the story. Duggan is not the stereotypical scientist-founder. He is a serial entrepreneur and investor who became Summit's chairman and co-CEO, alongside Dr. Maky Zanganeh as co-CEO and president. The two have essentially rebuilt Summit around the ivonescimab opportunity.

So Summit is a really interesting example of something we see repeatedly in biotech: the company that ultimately wins isn't necessarily the company that invented the molecule. Sometimes the winning company is the one that recognizes the opportunity, structures the deal, funds the clinical development, and figures out how to bring the asset into a new market.

Before we move on, it's worth pausing on Summit's stock market history — because it tells you a lot about how dramatically this company has transformed. Summit was founded in 2003 and originally listed on London's AIM market, then completed a U.S. Nasdaq listing in March 2015, raising $39.3 million at $9.90 per share — a modest raise for a company then focused on antibiotics and Duchenne muscular dystrophy. For years, the stock traded in relative obscurity. That changed almost overnight after the Akeso deal closed in early 2023. Summit's all-time high closing price hit $36.70 in April 2025 — a roughly 270% increase from its 2015 Nasdaq listing price — driven almost entirely by ivonescimab data. After the HARMONi-2 result showing ivonescimab outperforming Keytruda in China, Summit's shares skyrocketed nearly 600% over the following two years. That kind of move, from obscure antibiotic developer to one of biotech's most closely watched oncology plays, is almost unheard of — and it speaks directly to how high the stakes are around ivonescimab. The stock is now essentially a binary bet on whether that drug succeeds in the United States.

3. What Is Ivonescimab—and Why Is It Different?

Now let's get into the science.

Ivonescimab is a bispecific antibody, meaning that instead of being designed to recognize a single target, it is engineered to interact with two different biological targets. In this case, those targets are PD-1 and VEGF-A.

PD-1 is one of the major immune checkpoints in cancer. Tumors can essentially exploit the PD-1 pathway to suppress T-cell activity and evade the immune system. Drugs like pembrolizumab, or Keytruda, block PD-1 and help restore the immune system's ability to attack cancer. Keytruda became one of the most important cancer drugs in history because this mechanism works across multiple tumor types.

But tumors have another problem. They need blood vessels. Cancer cells require nutrients and oxygen to grow, and tumors can stimulate the formation of new blood vessels through angiogenesis. One of the central drivers of that process is VEGF, or vascular endothelial growth factor.

Instead of giving a patient a PD-1 inhibitor and a separate VEGF-targeting drug, what if you engineered a single antibody that could hit both pathways? That's the fundamental concept behind ivonescimab. According to Summit's filings, the molecule is designed to block PD-1's interaction with PD-L1 and PD-L2 while also blocking VEGF-A from binding its receptors, using Akeso's Tetrabody technology. The hypothesis is that you're not simply combining two mechanisms — you're potentially creating a molecule in which the mechanisms reinforce one another.

And that's what makes this more interesting than simply saying, "It's another PD-1 drug."

4. Why Keytruda Is the Target

To understand why Summit has attracted so much attention, you have to understand what it is trying to beat. Keytruda is one of the biggest blockbusters in pharmaceutical history. Merck's pembrolizumab has become foundational to modern oncology, particularly in lung cancer. So when a company comes along claiming that a new immunotherapy could outperform a PD-1 inhibitor, the stakes are enormous.

But ivonescimab isn't necessarily trying to replace Keytruda through the exact same mechanism. It's trying to move the mechanism forward.

Think about the evolution of cancer therapy. First, we had relatively nonspecific chemotherapy. Then targeted therapies allowed physicians to attack specific molecular abnormalities. Then immunotherapy changed the paradigm by helping the immune system attack tumors. And now we're increasingly seeing combinations of mechanisms being engineered into more sophisticated molecules. Bispecific antibodies are part of that next generation.

Instead of asking whether PD-1 blockade works, the question becomes: What happens if we combine immune activation with another mechanism that changes the tumor microenvironment?

In the HARMONi-2 study in previously untreated PD-L1-positive NSCLC, ivonescimab showed a significant progression-free survival advantage over pembrolizumab — that was the result that first put Summit on the map. Then in HARMONi-6, ivonescimab plus chemotherapy produced a statistically significant overall survival benefit compared with tislelizumab plus chemotherapy, with a median OS of 27.9 months versus 23.7 months — a 34% reduction in the risk of death.

And suddenly the question changed. Instead of asking, "Is this an interesting bispecific?" people started asking: "Could this actually become a Keytruda competitor?" That's a much bigger conversation.

5. The China-to-U.S. Story

But there's another layer to this story that I think is just as important as the science.

Ivonescimab is a product of Chinese biotech innovation. Akeso developed the molecule in China, ran major clinical studies there, and generated some of the earliest compelling clinical data. Summit then licensed the rights to develop the molecule in Western markets.

This represents a major shift in how global drug development works. For decades, the dominant model was essentially Western pharmaceutical companies discovering drugs, developing them globally, and then conducting additional studies in Asian populations. Now we're seeing the reverse. A Chinese biotech develops a drug. Chinese clinical trials generate the initial evidence. A Western biotech licenses the asset. And the Western company then has to demonstrate that the results translate into North American and European patients.

That's exactly the challenge Summit now faces — and it is not theoretical.

In the global Phase 3 HARMONi trial, ivonescimab plus chemotherapy demonstrated a significant progression-free survival benefit with a hazard ratio of 0.52 and median PFS of 6.8 versus 4.4 months. However, PFS among European and North American patients was notably shorter than among Asian patients, with a hazard ratio of 0.67 in Western patients compared to 0.45 in Asian patients — a regional gap that analysts and regulators have scrutinized closely.

In a more recent updated survival analysis using a June 2026 data cutoff, the overall survival hazard ratio in Western patients improved to 0.76, compared to 0.84 at the September 2025 cutoff, suggesting that with longer follow-up, the benefit in Western patients continues to trend in a favorable direction. But those results do not yet carry statistical significance — and that is the central regulatory question Summit faces heading into November.

If ivonescimab succeeds in the United States, it doesn't just validate one drug. It helps validate a new model of China-originated innovation being commercialized globally.

6. The Clinical Program—and the Massive Opportunity

Summit's pipeline is surprisingly concentrated. The company is essentially building its future around ivonescimab, but it's developing the drug across multiple cancers and treatment settings.

In non-small cell lung cancer, Summit has programs including HARMONi, which evaluates ivonescimab with chemotherapy in EGFR-mutated disease after third-generation EGFR TKIs — the program underlying its current FDA application; HARMONi-3, which evaluates the drug with chemotherapy versus pembrolizumab plus chemotherapy in first-line metastatic NSCLC; and HARMONi-7, which is studying ivonescimab monotherapy against pembrolizumab in first-line patients with high PD-L1 expression in a global trial. Summit is also developing ivonescimab in first-line colorectal cancer through HARMONi-GI3.

And the commercial opportunity is enormous. Lung cancer is one of the largest cancer markets in the world, and NSCLC represents the majority of lung cancer cases. If ivonescimab can establish itself across multiple lines of therapy and patient populations, Summit could potentially compete for a market that currently generates enormous revenue for Merck and other pharmaceutical companies.

In July 2026, Summit entered a clinical collaboration with Arcus Biosciences to evaluate ivonescimab in combination with casdatifan, a HIF-2α inhibitor, in clear cell renal cell carcinoma. So the long-term strategy is increasingly clear. Ivonescimab may start as a lung-cancer drug. But Summit wants to turn it into a platform-like oncology franchise that can be combined with other mechanisms and moved into other solid tumors. And that is where the potential valuation becomes much larger.

7. But Here's the Problem: The Data Are Getting More Complicated

Now we need to talk about the part of the story that is easy to overlook if you're only reading the bullish headlines. Because Summit's story is not simply "new drug beats Keytruda." The data are complicated.

HARMONi-6 produced an impressive overall survival result with a 34% reduction in risk of death against tislelizumab plus chemotherapy. But the story in the global HARMONi trial — the one actually under FDA review — is more nuanced. The trial showed that Western patients experienced notably shorter progression-free survival than Asian patients. While the updated survival analysis has trended more favorably in Western patients with longer follow-up, the OS data in the Western subgroup does not yet reach statistical significance — and the FDA had explicitly requested statistically significant OS data to support the filing.

That doesn't mean ivonescimab doesn't work. It means the question has become more nuanced. How durable is the benefit? How broadly does it apply in Western populations? What endpoint will regulators ultimately require?

Those are very different questions from simply asking whether the drug produces tumor responses. And this is why oncology is so difficult. A drug can produce an impressive progression-free survival result without necessarily delivering the same magnitude of overall survival benefit. And regulators increasingly care about whether the clinical benefit is meaningful to patients. Summit is awaiting an FDA decision on November 14, 2026 — and the next few months are perhaps the most consequential in the company's history.

8. The Business Model—and the Risk of Betting Everything on One Drug

There's another fascinating aspect to Summit: concentration risk. Unlike a large pharmaceutical company with 30 or 50 clinical programs, Summit's story is overwhelmingly centered on ivonescimab. That creates enormous upside if the drug works. But it also creates enormous downside if the program disappoints.

As of June 30, 2026, Summit reported approximately $690.7 million in cash and investments and no debt. The company is spending heavily on clinical development, with second-quarter 2026 GAAP operating expenses of about $220.5 million, including $157.7 million in R&D. So this isn't a company sitting on a commercialized blockbuster generating billions of dollars in cash flow. It's a clinical-stage biotech spending aggressively to get its lead asset through the regulatory process.

And the economics of the Akeso deal are important context: Summit paid $500 million upfront for its initial territory rights, with a total potential deal value of up to $5 billion including milestones, plus low double-digit royalties on net sales. That means if ivonescimab becomes a blockbuster, Akeso is going to participate meaningfully in the economics.

And I actually think that's one of the most interesting features of the deal. Summit didn't have to discover the molecule. Akeso didn't have to build a giant U.S. commercial organization. Instead, the two companies divided the work. Akeso brought the molecule and China development expertise. Summit brought Western development, capital, regulatory strategy, and commercialization. That's a model we're probably going to see more frequently as Chinese biotech becomes increasingly important to global drug development.

9. Lessons from Summit

And ultimately, that's why Summit is such a fascinating company to follow. The story isn't just about whether ivonescimab beats Keytruda. It's about several major trends happening simultaneously.

First, bispecific antibodies are becoming an increasingly important modality in oncology. Rather than simply developing one-target antibodies, companies are engineering molecules capable of interacting with multiple biological pathways at once. Second, the PD-1/VEGF combination is becoming an increasingly competitive area — Merck itself has a PD-1/VEGF bispecific, MK-2010, in early clinical development. Third, China is becoming an increasingly important source of innovative drug candidates rather than simply a manufacturing destination or clinical-trial market. Fourth, pharmaceutical companies are increasingly willing to license assets rather than discover everything internally.

Summit is a great example of all four trends simultaneously.

The company didn't discover ivonescimab. It didn't invent the PD-1 mechanism. It didn't invent VEGF inhibition. It didn't invent bispecific antibodies. What it did was identify a potentially valuable combination of those technologies, partner with the company that had developed it, and build a global development strategy around it. That's innovation through orchestration. And I think that is going to become increasingly important as the global biotech ecosystem becomes more interconnected.

Closing: Can Summit Actually Take on Keytruda?

So, where does that leave us?

Summit Therapeutics has one of the most compelling oncology stories in biotech right now. It took a company that was once centered on an antibiotic program, pivoted dramatically, licensed a promising Chinese-developed bispecific antibody, and built an aggressive global clinical-development program around it.

Ivonescimab has already generated impressive data — including a significant overall survival benefit against tislelizumab plus chemotherapy in a Phase 3 Chinese study — and updated global trial data suggests the mechanism can work beyond China. But the story is not finished.

The biggest question is whether the drug can consistently reproduce its clinical benefit across different populations and treatment settings. The second is whether regulators will consider the evidence sufficient for approval on November 14, 2026. The third is whether Summit can turn ivonescimab into a broad oncology franchise rather than a single indication. And the fourth is whether this entire story represents the beginning of something much bigger — a world in which some of the most important drugs in Western markets originate from biotech companies in China and are then licensed to Western companies for global development.

Because if ivonescimab succeeds, Summit won't just have created a valuable cancer drug. It will have demonstrated a new model for how biotech innovation moves around the world.

And perhaps the most interesting question isn't even whether ivonescimab can beat Keytruda. It's whether the next generation of blockbuster drugs will come from the companies we aren't looking at today — and whether the smartest pharmaceutical companies will be the ones capable of finding those assets wherever in the world they are being developed.

That's the real Summit Therapeutics story.

This has been Petri Dish Perspectives. I'm Manead. Thanks for listening. See you next Thursday. Goodbye.

References

1. https://smmttx.com/overview/default.aspx 
2. www.wikipedia.org
3. https://endpoints.news/ 
4. https://finance.yahoo.com/ 

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