ABEL Bio's Triple Threat: ESMO 2026 Unveils Progress and Challenges
Despite showing significant improvements in tumor response rate and progression-free survival, ABEL Bio's (298380) lead drug candidate, Tovesimig, failed to demonstrate an overall survival benefit in its quest to become a breakthrough treatment for bile duct cancer. This development has raised questions about its approval process in the United States.
In a contrasting development, Zivastomig, another dual-antibody therapy in ABEL Bio's pipeline, is gaining momentum in its clinical development for esophageal cancer. The therapy has shown promising tumor reduction responses in patients with low expression levels, a group typically not eligible for targeted therapies. This breakthrough paves the way for a swift initiation of Phase 3 trials.
Meanwhile, Rajstomig, the third drug candidate, offers a potential solution to mitigate severe adverse reactions by adjusting the dosing interval.
Each of these three candidates is at a different stage of development and is being evaluated against distinct metrics. Tovesimig is currently reviewing its approval strategy based on late-stage clinical results, while Zivastomig and Rajstomig are in the process of finalizing the dosage and administration methods for subsequent development stages.
Tobesimig's Clinical Trial Results: Meeting Key Endpoints, But Survival Duration Remains a Challenge
The COMPANION-002 phase 2/3 clinical trial for Tobesimig, announced by its U.S. partner company Compesthetics on June 24th, enrolled 168 patients with progressive biliary cancer who had received prior treatment.
The objective response rate (ORR), which measures the percentage of patients with a significant reduction in tumor size, was 18.0% in the Tobesimig plus paclitaxel combination arm, compared to 5.3% in the paclitaxel monotherapy arm. The median progression-free survival (PFS), representing the time until cancer progression or death, was 4.7 months in the combination arm, significantly surpassing the 2.6 months in the control arm. The risk of disease progression or death was 56% lower in the combination group compared to the control.
These results demonstrated statistically significant improvements in both the primary endpoint of ORR and the key secondary endpoint of PFS.
Dr. Nirofer Azad, the clinical trial presenter from Johns Hopkins University, stated, "The significant improvements in response rate and progression-free survival, along with the durability of response and disease control, are encouraging for patients in this treatment setting. We also observed anti-tumor activity in patients who transitioned to Tobesimig after progressing on paclitaxel monotherapy."
Overall Survival and Cross-Over Treatment
The median overall survival (OS), a measure of the duration of patient survival post-treatment, showed no significant difference between the combination group (8.9 months) and the control group (9.4 months).
When interpreting these results, it is crucial to consider the cross-over treatment. Among the 57 patients in the control group, 31 (54%) crossed over to the Tovasemig combination therapy after disease progression. Consequently, approximately 85% of the total patient population received Tovasemig during the study period.
The post-hoc cross-over adjusted analysis, presented by Compass Therapeutics at the conference and in the international journal *Journal of Clinical Oncology (JCO)*, estimated an overall survival hazard ratio (HR) of 0.85. However, this did not reach statistical significance (p=0.53).
*Source: Compass Therapeutics, Tovasemig COMPANION-002 Clinical Trial Design*
While significant improvements were observed in tumor response rate and progression-free survival, the study did not demonstrate an extension in overall survival. The U.S. Food and Drug Administration (FDA) recommended additional trials to prove survival benefit in September. Compass Therapeutics maintains its position to pursue regulatory approval based on the existing clinical data.
Tovesimab's Approval Timeline and ABL Bio's Milestone Payments Hang in the Balance
#### Zivastomig Shows Promise in Low-Expression Patient Group, Paving the Way for Phase 3
Zivastomig (ABL111), an innovative dual-antibody therapy jointly developed by ABL Bio and Novabridge Biosciences, simultaneously targets Claudin18.2 on cancer cells and 4-1BB on immune cells.
The recently released additional analysis of the Phase 1b trial, which included a total of 71 participants, revealed promising results. Among the 29 evaluable patients in the selected 8mg/kg dose group, 23 showed a tumor reduction response, achieving an objective response rate of 79%. The disease control rate stood at an impressive 97%, with a median response duration of 15.2 months.
Notably, the study's findings highlight the therapy's effectiveness in the low-expression patient group. Of the 12 patients with a Claudin18.2 expression rate of 1-74%, 9 (75%) exhibited tumor reduction. In the group with an expression rate of 75% or higher, 14 out of 17 patients (82%) responded positively.
Wall Street's Take on the Latest Financial News
Breaking Down the Financial Impact: Claudin18.2 Targeted Therapy
The recently approved Claudin18.2 targeted therapy, Viloy, targets patients with a protein expression level above a certain threshold in at least 75% of their tumor cells, as determined by specific testing criteria.
If Zivastomig demonstrates its effectiveness in subsequent trials for patients with low expression levels, it could potentially offer a new treatment option for those who do not meet the existing criteria for targeted therapies. However, due to the differing clinical populations and assessment criteria between the two therapies, direct comparisons of treatment scope and efficacy cannot be made solely based on these figures.
Samuel Klemperner, a clinical researcher at Massachusetts General Hospital, explained, "What stands out in this additional analysis is not only the sustained treatment efficacy observed through long-term follow-up but also the strong and consistent efficacy results seen in a broad range of Claudin18.2 expression levels, including those with very low expression."
This early study combines Zivastomig with nivolumab and chemotherapy, making it challenging to isolate the treatment contribution of Zivastomig alone, as there was no separate control group. Additionally, the 79% response rate includes preliminary responses yet to be confirmed.
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Safety Profile
The safety analysis revealed no reported grade 4-5 treatment-related adverse events attributed to Zivastomig.
ABBL Bio and Novabridge have selected an 8mg/kg dose for further development. Global Phase 2 trials are currently underway, and key design discussions with the FDA for a pivotal Phase 3 trial have been completed.
In the upcoming Phase 3 trials, it will be crucial to demonstrate that the high response rates observed in early-stage trials are reproducible in larger patient populations, and that there is a clinical benefit compared to existing standard treatments.
Reduced Severe Adverse Reactions in 6-Week Dosing Interval
Ragistomig (ABL503), a dual-targeting immunotherapy for PD-L1 and 4-1BB, has shown promising results. While 4-1BB-targeting therapies can enhance the anti-cancer activity of immune cells, managing liver toxicity remains a key challenge in the development process.
The recently disclosed Phase 1 trial data revealed a lower incidence of severe adverse reactions in patients with a 6-week dosing interval compared to the standard 2-week interval.
This development could potentially address one of the key challenges in immunotherapy, as longer dosing intervals may reduce the risk of severe adverse events. However, further investigation is required to determine the optimal dosing strategy and its impact on clinical outcomes.
Late-stage Clinical Trial Results: AB9390-NVB302 Combination Therapy
Treatment-Related Adverse Events
The incidence of grade 3 or higher treatment-related adverse events was 51.6% in the 2-week interval dosing group and 26.2% in the 6-week interval dosing group. Significant differences were also observed in the rate of severe liver function test abnormalities, with 35.5% and 11.9% respectively.
Antitumor Response and Efficacy
Despite the extended dosing interval, antitumor response was still evident in the patient group. The objective response rate was 11.8% (2/17) for the 6-week interval 3mg/kg dosing group and 21.1% (4/19) for the 5mg/kg dosing group.
Out of the 13 overall responders, 11 were patients who had either not responded to previous PD-1/PD-L1 immune checkpoint inhibitor therapy or had relapsed after treatment.
Implications and Future Development
These results suggest the potential to maintain antitumor activity while managing toxicity burden through dose interval adjustments. However, as this trial was not a randomized assignment comparison of dosing intervals, the difference in adverse event incidence cannot be solely attributed to the dosing interval effect.
AB9390-NVB302 is currently being evaluated in combination with a PD-1 inhibitor. Further development should focus on confirming whether the improved safety profile observed in monotherapy is maintained in combination therapy.
Late-Stage Trial Results Spark Market Volatility
The recent ESMO presentation unveiled critical uncertainties surrounding Tovesimib's approval and highlighted the potential for further development of Zivastomig and Rajastomig. These drugs face distinct challenges in their respective development pipelines.
Tovesimib, despite its promising potential, must navigate through subsequent negotiations with the FDA and address lingering uncertainties. Meanwhile, Zivastomig aims to replicate its efficacy in the global Phase 3 trial, and Rajastomig focuses on confirming its safety profile in combination therapy.
These developments have left investors with a cautious outlook, as each drug's path to commercialization faces unique hurdles. The market will closely monitor the progress of these trials, with potential implications for the companies' future growth and valuation.
- Tovesimib: FDA discussions and regulatory approval remain key milestones.
- Zivastomig: Efficacy replication in global trials is crucial for its advancement.
- Rajastomig: Safety confirmation in combination therapy is essential for its next phase.
As the pharmaceutical sector navigates these late-stage trials, investors should brace for potential margin call liquidations and late-session selling pressure, especially if these drugs fail to meet expectations. The yield rates and commercialization potential of these treatments will be under intense scrutiny in the coming months.
