Paul Moore
Analyst · Yigal Nochomovitz of Citigroup. Your line is not open
Thanks, Leone, and good afternoon everyone. As previously mentioned, we are pleased to have attended yet another productive AACR for Zymeworks this year with six posters presented by our team. The breadth of preclinical data presented across both our innovative multi-specific antibodies and ADC programs highlights not just scientific progress, but the thoughtful diversification of our R&D strategy. Among the highlights, we are especially encouraged by the preclinical data presented on ZW209, our most recent IND nominated oncology candidate with a planned IND submission in the first half of 2026. ZW209 is a trispecific T cell engager targeting DLL3, a protein expressed on the cell surface of small cell lung cancer and other aggressive neuroendocrine tumors. This trispecific T cell engager incorporates CD28 co-stimulation and has shown potent antitumor activity in preclinical models including small cell lung cancer. These cancers are notoriously hard to treat and while there's been some success with the approval of tarlatamab in small cell lung cancer, ensuring the benefit of a bispecific approach for solid tumors, there is a clear need for next generation molecules that can improve the standard of care with broader and more durable responses. That's where we believe ZW209 stands out. We've designed 209 using our TriTCE Co-Stim platform combined with our proprietary Azymetric and EFECT technologies to activate T cells in a more controlled and effective way. A key feature of our design is the obligate nature of CD28 engagement. CD28 binding by 209 occurs only in the presence of simultaneous CD3 binding. This is shown clearly in the top left panel where control molecules with either CD3 or CD28 binding knocked out demonstrate that CD28's contribution is conditional on CD3 engagement. This obligate co-stimulation limits potential for unwanted T cell cross linking, or Fratricide, an important safety and specificity advantage of our TriTCE platform. Furthermore, the obligate nature of tumor engagement via DLL3 ensures that 209's activity is precisely focused where it's needed. Additional data in our poster further supports this specificity. What's particularly encouraging is the strength and durability of the response we're seeing in preclinical models. As shown in the middle top panel, the addition of CD28 enhances T cell fitness and robustness in the presence of DLL3 positive tumor cells. Compared to control molecules lacking CD28 engagement and versus the clinical benchmark AMG757 or tarlatamab 209 provides more sustained tumor cytotoxicity across repeated rounds of stimulation, which is accompanied by expansion of T cells with memory phenotype.
, : Beyond the data shown here, our AACR poster further characterizes safety profile of 209 incorporating results from a dedicated mouse model of cytokine release syndrome complementary in vitro cytokine release assays studies conducted in non-human primates. In the non-human primate studies, repeat dosing at 10 mgs/kg was well tolerated and 209 demonstrated an antibody like pharmacokinetic profile, a characteristics that can be associated with more predictable behavior in clinical settings. Taken together, these data reinforce the significance of the CD28 arm in driving deeper and more durable T cell responses while maintaining stringent control and safety through obligate engagement of both T cells and DLL3 expressing tumor cells. We're excited about the trajectory of 209 as we work towards IND submission in the first half of 2026. In our earlier R&D programs, we continue to focus on novel targets and customized modalities that we believe offer meaningful opportunities for therapeutic innovation. Two of these ADC programs revealed at AACR focus on Ly6E and PTK7, both tumor associated antigens with limited expression in normal tissues and broad relevance across difficult to treat solid tumors. While we haven't provided guidance on IND timelines for these programs, we continue to explore opportunities on how and when to advance these programs either internally or through thoughtful collaborations. For those of you less familiar Ly6E is overexpressed in multiple indications of high unmet needed including non-small cell lung cancer, triple-negative breast cancer, head and neck cancer and GI cancers. Notably, Ly6E is expressed in the majority of patient samples across these indications suggesting a potential for broad applicability while maintaining target specificity. Clinical validation of Ly6E as an ADC target has been reported by clinical stage benchmark DLYE5953A and MMAE DAR4 based ADC from Genentech in breast cancer and non-small cell lung cancer. 327, which targets Ly6E, utilizes Zymeworks's novel 6519 payload with a drug antibody ratio of 8, which enables strong cytotoxicity across a range of solid tumor indications. Consistent with our general approach to ADC design and care also in selection of the antibody targeting arm, 327 utilizes a novel humanized IgG1 antibody, which exhibits markedly superior Ly6E binding internalization and spheroid penetration relative to the Ly6E antibody incorporated in the prior clinical stage program. As shown on the right, 327 has demonstrated consistent in vitro target specific cytotoxicity across multiple cancer types, this activity is observed in these broad range of indications and is consistently superior to the benchmark with a likewise improvement also observed in xenograft models in vivo. These findings underscore the potential of 327 to deliver more consistent and deeper response in Ly6E expressing cancers regardless of baseline expression levels, an important consideration given the heterogeneity often seen in tumors. On the safety side, 327 was well tolerated in a non-GLP tox study in non-human primates exposure levels exceeded dose projected to be efficacious and the maximum tolerated dose was established at or above 60 mgs/kg. Observed clinical effects were limited to transient reductions in body weight and food intake post-dosing with no serious adverse events. Altogether, these data built a compelling case for 327 as a differentiated therapeutic candidate targeting Ly6E and a first in class opportunity for Zymeworks. Moving on to Slide 12, PTK7 is a transmembrane protein that is overexpressed in a range of solid tumors including non-small cell lung, triple-negative breast, ovarian, esophageal, colorectal, head and neck and cervical cancers. Previous clinical data with PTK7 targeting ADCs have demonstrated evidence of anti-tumor activity, albeit limited in several of these indications, reinforcing PTK7 as a validated ADC target. Structurally, PTK7 offers a large multi-domain extracellular region that enables the development of antibodies against distinct non-overlapping epitopes and the opportunity to develop biparatopic ADCs as a solution to enhance payload delivery. Depending on the target antigen, monoparatopic ADCs may not deliver as much payload into cancer cells as biparatopic ADCs and this may have contributed to the modest activity seen with previous PTK7 targeting ADCs, thus opening the door to biparatopic formats and other modular based approaches including next generation ADCs targeting PTK7. Biparatopic antibodies offer several advantages over traditional monoparatopic designs. By binding two distinct sites in the same antigen, they can enhance receptor clustering, increase cell surface retention, improve internalization factors that are particularly important in ADC design. These properties could translate to more efficient payload delivery, increased cytotoxicity and increased cytotoxicity in tumor cells. Importantly, we bring deep experience in designing, developing and advancing biparatopic antibodies through our work with zanidatamab. Zanidatamab, a biparatopic HER2 target antibody, has demonstrated meaningful clinical activity and validated the potential of biparatopic approaches as well as providing clinical validation for our proprietary Azymetric platform not just from a biological standpoint but also in the terms of manufacturability. This gives us confidence that our biparatopic PTK7 ADC program can benefit from both proven mechanistic advantages and our deep experience in utilizing our established scalable platform. In preclinical studies, we've observed improved antibody binding and higher internalization in PTK7 expressing cell lines compared to conventional formats. This enhanced uptake has resulted in greater payload delivery and corresponding cytotoxicity activity, supporting the value of biparatopic targeting in this context. From a pharmacokinetic and tolerability standpoint, the data are also compelling. In non-human primates, our PTK7 biparatopic ADC was well tolerated at doses up to 60 mgs/kg no mortality or adverse clinical signs were observed and any change in hematology or chemistry were minor and transient. Our mixed effects were consistent with expected class effects and not considered dose limiting. These findings suggest that our biparatopic ADC may offer a differentiated profile, particularly in tumors where PTK7 is broadly expressed or where internalization has historically been a limiting factor. We look forward to continued optimization work in evaluating this approach across relevant clinical model, preclinical models. Lastly, moving on to our poster presentation on ZW171, a mesothelin targeting T cell engager demonstrating enhanced safety and antitumor activity in a range of mesothelin expressing cancers. As you know, we have reported the first patient dosed in October 2024 for our first in human Phase 1 trial, which continues across sites in the U.S., UK and South Korea and I'll touch on the ongoing trial in a couple of slides. 171 is engineered with a lower affinity CD3 binding arm, which is designed to reduce the likelihood of indiscriminate T cell activation and cytokine release especially in the absence of high mesothelin expression. Many T cell engagers with high CD3 affinity like earlier generation one plus one formats have triggered systemic CRS because they activate T cells even when target engagement is weak or off tumor. In head to head preclinical comparisons, 171 has demonstrated superior cytotoxicity versus other next generation mesothelin targeting bispecifics. Importantly, this enhanced tumor cell killing comes with improved cell activity. We've observed reduced non-specific T cell binding relative to other programs in this space, a feature that may contribute to a more favorable safety profile. In the middle column, you can see that 171 exhibits selective and high affinity binding to tumor cells expressing high levels of mesothelin while showing minimal binding to cells with low mesothelin expression. Importantly, 171 maintains low affinity for CD3, which is a deliberate design choice to reduce off target T cell activation and improve safety. This profile underscores its ability to preferentially target tumors, while sparing normal tissues with minimal mesothelin expression. Moving to the cytotoxicity data on the right, 171 continues to demonstrate potent and selective tumor cell killing in high mesothelin high settings, but not in low mesothelin expressing cells compared to benchmark molecules including AMG305, CT95 and the JNJ bispecific comparator. ZW171 consistently shows equal or superior cytotoxicity across a panel of tumor cell lines with varying levels of mesothelin expression, particularly at low effector to target ratios, which more closely reflects conditions in the tumor microenvironment. As you can see on the left hand side of this slide, in a large panel of tumor cell lines including those that shed soluble mesothelin, 171 maintained strong antitumor potency. Notably, no correlation was observed between the amount of shed mesothelin and 171's efficacy, underscoring the robustness of its mechanism of action. These findings support our hypothesis that our two plus one design sustains activity in the presence of shed mesothelin through avidity dependent mesothelin binding on high-mid expressing tumor cells. What also stands out, as depicted in the graphs on the right hand side of the slide, is that 171 also demonstrated cytotoxicity, T cell activation and cytokine release in more complex translationally relevant patient derived xenograft models containing endogenous tumor infiltrating lymphocytes as well as in vivo xenograft models. These data support further the potential of 171 to drive meaningful responses in mesothelin expressing tumors, particularly in challenging tumor microenvironments. Together, these data reinforce our confidence in 171's potential to deliver meaningful therapeutic benefit while demonstrating a favorable tolerability profile. With our Phase 1 clinical trials in mind, both studies for 171 and 191 remain on track and are recruiting well across sites. This slide highlights the breakdown of currently activated clinical sites by geographic region. Our global clinical trial footprint is a key component of our strategy to move efficiently through early development. By engaging sites across multiple geographies within and outside the United States, we're able to maintain momentum in enrollment while optimizing the use of clinical supply and supporting streamlined operational execution. Looking ahead, we do plan to present trial and progress posters for both 171 and 191 at upcoming peer-reviewed medical conferences in the second quarter, as Leone mentioned earlier. And with that I will hand over to Ken to conclude today's call and open up the call for Q&A.