On September 16, 2024 Summit Therapeutics Inc. (NASDAQ: SMMT) ("Summit," "we," or the "Company") reported that data for the novel, potential first-in-class investigational bispecific antibody, ivonescimab, was presented at the 2024 European Society for Medical Oncology Annual Meeting (ESMO 2024) in Barcelona, Spain, including two presentations and one poster featuring updated ivonescimab data in advanced triple-negative breast cancer (TNBC), recurrent / metastatic head and neck squamous cell carcinoma (HNSCC), and metastatic microsatellite-stable (MSS) colorectal cancer (CRC) (Press release, Summit Therapeutics, SEP 16, 2024, View Source [SID1234646686]). Each trial from which the data was generated was a Phase II study conducted in China sponsored by Akeso Inc. (HKEX Code: 9926.HK) with data generated and analyzed by Akeso.
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Based on the results of these Phase II data sets as well as data announced earlier in 2024, including early-stage non-small cell lung cancer and biliary tract cancer, Summit intends to explore further clinical development of ivonescimab in solid tumor settings outside of metastatic non-small cell lung cancer, the Company’s current area of focus in its Phase III clinical trials.
Metastatic MSS Colorectal Cancer
The first oral presentation was presented by Dr. Yanhong Deng, Sun Yat-Sen University. The presentation was entitled, The efficacy and safety of ivonescimab with or without ligufalimab in combination with FOLFOXIRI (chemotherapy) as first-line treatment for metastatic CRC, presenting the current data from AK112-206, included data from this single-region (China), multicenter, open-label, Phase II randomized study of patients with first-line metastatic MSS CRC (NCT05382442).
The study was designed to assess patients who were randomly assigned to receive ivonescimab plus FOLFOXIRI with or without ligufalimab (anti-CD47 monoclonal antibody). Note that ligufalimab, or AK117, is Akeso’s proprietary, investigational product that is not approved by any regulatory authority, and to which Summit does not have any license or ownership rights.
As of February 29, 2024, 22 patients received ivonescimab plus FOLFOXIRI ("Group A" with median follow-up time of 9 months); 18 patients received ivonescimab plus ligufalimab plus FOLFOXIRI ("Group B" with median follow-up time of 9.6 months).
Ivonescimab + Chemo
(Group A) (n = 22)
Ivonescimab + Ligufalimab + Chemo (Group B) (n = 18)a
Overall response rate
81.8%
(95% CI: 59.7, 94.8)
88.2%
(95% CI: 63.6, 98.5)
Disease control rate
100%
(95% CI: 84.6, 100)
100%
(95% CI: 80.5, 100)
Median PFS
NR
NR
9-month PFS rate
81.4%
(95% CI: 52.1, 93.7)
86.2%
(95% CI: 55.0, 96.4)
Serious TRAE
22.7%
11.1%
TRAEs Leading to Permanent Discontinuation
0
5.6%
a As of data cutoff, one patient in Group B had not yet had a post-baseline tumor assessment; Group B response and control rates based on n=17.
All patients in both Group A and Group B experienced a reduction in their tumor burden compared to their baseline tumor assessment. The overall response rate and the disease control rate for the 39 patients who had a least one post-baseline tumor assessment was 84.6% and 100%, respectively. Median progression-free survival was not reached in either group at the time of this analysis.
The safety profile in this Phase II study was acceptable and manageable. No patients receiving ivonescimab plus FOLFOXIRI and one patient receiving ivonescimab plus ligufalimab plus FOLFOXIRI permanently discontinued drug treatment due to treatment-related adverse events. The most common TRAEs were anemia, proteinuria, white blood cell count decreases, and neutrophil count decreases in this Phase II data set.
Advanced Triple Negative Breast Cancer
The second oral presentation was presented by Dr. Xiaojia Wang, Zhejiang Cancer Hospital. The presentation was entitled, The safety and efficacy of ivonescimab in combination with chemotherapy as first-line (1L) treatment for triple-negative breast cancer (TNBC), presenting the current data from AK117-203, included data from this single-region (China), multicenter, open-label, Phase II study (NCT05227664).
The results presented were from the portion of the study intended to assess patients who received ivonescimab plus chemotherapy (either paclitaxel or nab-paclitaxel) with locally advanced or metastatic TNBC.
As of May 31, 2024, 30 patients received ivonescimab plus chemotherapy with median follow-up time of 10.2 months. Sixty percent of patients had previously received taxane-based chemotherapy in either the neoadjuvant or adjuvant setting in this Phase II data set.
Overall
(n = 30)a
Overall response rate
72.4%
Disease control rate
100%
Median PFS
9.3 months
(95% CI: 6.24, NE)
Serious TRAE
30%
TRAEs Leading to Permanent Discontinuation
0
PD-L1 CPS >10
(n = 6)
PD-L1 CPS <10
(n = 24)a
PD-L1 CPS <1
(n = 16)a
Overall response rate
83.3%
69.6%
86.7%
Disease control rate
100%
100%
100%
Median PFS
NR
(5.36, NE)
9.3 months
(5.55, NE)
9.3 months
(5.26, NE)
a As of data cutoff, one patient with a PD-L1 CPS expression of 0 had not yet had a post-baseline tumor assessment; Overall patients, PD-L1 CPS <10, and PD-L1 CPS <1 response and control rates based on n=29, n=23, and n=15, respectively.
All patients experienced a reduction in their tumor burden compared to their baseline tumor assessment. The overall response rate and the disease control rate for the 29 patients who had at least one post-baseline tumor assessment were 72.4% and 100%, respectively. Median progression-free survival was 9.30 months as the time of this analysis.
The safety profile in this Phase II study was acceptable and manageable. No patients receiving ivonescimab plus chemotherapy permanently discontinued drug treatment due to treatment-related adverse events. The most common TRAEs were white blood cell count decreases, ALT increases, alopecia, AST increases, and neutrophil count decreases in this Phase II data set.
Recurrent / Metastatic Head and Neck Squamous Cell Carcinoma
The third data presentation was a poster from Dr. Xiaozhong Chen, et al. The poster was entitled, Evaluation of the safety and efficacy of ivonescimab in combination with ligufalimab (anti-CD47) as first-line treatment for PD-L1 positive recurrent/metastasis HNSCC, presenting current data from a portion of AK117-201. The data is from a single-region (China), multicenter, open-label, Phase II study (NCT05229497).
The results presented were from the portion of the study intended to assess patients who received ivonescimab with or without ligufalimab (anti-CD47) with PD-L1 positive, locally advanced or metastatic recurrent / metastatic head and neck squamous cell carcinoma.
As of March 19, 2024, 10 patients received ivonescimab (median follow-up: 3.3 months) and 20 patients received ivonescimab plus ligufalimab (median follow-up 4.1 months). Four of 10 patients receiving ivonescimab had a PD-L1 CPS of 1-20; nine of 20 patients administered ivonescimab plus ligufalimab had a PD-L1 CPS of 1-20; the remaining patients in each arm had a PD-L1 CPS >20.
Ivonescimab
(n=10)
Ivonescimab + Ligufalimab
(n = 20)
Overall response rate
30.0%
60.0%
Disease control rate
80.0%
90.0%
Median PFS
5.0 months
7.1 months
6-month PFS rate
NR
71.8%
Serious TRAE
0
5.0%
TRAEs Leading to Permanent Discontinuation
0
0
The overall response rate and the disease control rate for the 30 patients was 50.0% and 86.7%, respectively.
The safety profile in this Phase II study was acceptable and manageable. No patients receiving ivonescimab or ivonescimab plus ligufalimab in this data set permanently discontinued drug treatment due to treatment-related adverse events. The most common TRAEs in this Phase II data set were proteinuria, dermatitis acneiform (each observed in both arms), and hypothyroidism (observed only in the ivonescimab plus ligufalimab arm).
About Ivonescimab
Ivonescimab, known as SMT112 in Summit’s license territories, the United States, Canada, Europe, Japan, Latin America, including Mexico and all countries in Central America, South America, and the Caribbean, the Middle East, and Africa, and as AK112 in China and Australia, is a novel, potential first-in-class investigational bispecific antibody combining the effects of immunotherapy via a blockade of PD-1 with the anti-angiogenesis effects associated with blocking VEGF into a single molecule. Ivonescimab displays unique cooperative binding to each of its intended targets with multifold higher affinity when in the presence of both PD-1 and VEGF.
This could differentiate ivonescimab as there is potentially higher expression (presence) of both PD-1 and VEGF in tumor tissue and the tumor microenvironment (TME) as compared to normal tissue in the body. Ivonescimab’s tetravalent structure (four binding sites) enables higher avidity (accumulated strength of multiple binding interactions) in the TME with over 18-fold increased binding affinity to PD-1 in the presence of VEGF in vitro, and over 4-times increased binding affinity to VEGF in the presence of PD-1 in vitro (Zhong, et al, SITC (Free SITC Whitepaper), 2023). This tetravalent structure, the intentional novel design of the molecule, and bringing these two targets into a single bispecific antibody with cooperative binding qualities have the potential to direct ivonescimab to the tumor tissue versus healthy tissue. The intent of this design, together with a half-life of 6 to 7 days (Zhong, et al, SITC (Free SITC Whitepaper), 2023), is to improve upon previously established efficacy thresholds, in addition to side effects and safety profiles associated with these targets.
Ivonescimab was engineered by Akeso Inc. (HKEX Code: 9926.HK) and is currently engaged in multiple Phase III clinical trials. Over 1,800 patients have been treated with ivonescimab in clinical studies globally.
Summit has begun its clinical development of ivonescimab in non-small cell lung cancer (NSCLC), commencing enrollment in 2023 in two multi-regional Phase III clinical trials, HARMONi and HARMONi-3, with a plan to initiate HARMONi-7 in early 2025.
HARMONi is a Phase III clinical trial which intends to evaluate ivonescimab combined with chemotherapy compared to placebo plus chemotherapy in patients with EGFR-mutated, locally advanced or metastatic non-squamous NSCLC who have progressed after treatment with a 3rd generation EGFR TKI (e.g., osimertinib).
HARMONi-3 is a Phase III clinical trial which is designed to evaluate ivonescimab combined with chemotherapy compared to pembrolizumab combined with chemotherapy in patients with first-line metastatic squamous NSCLC.
HARMONi-7 is a planned Phase III clinical trial which is intended to evaluate ivonescimab monotherapy compared to pembrolizumab monotherapy in patients with first-line metastatic NSCLC whose tumors have high PD-L1 expression (PD-L1 TPS > 50%).
In addition, Akeso has recently had positive read-outs in two single-region (China), randomized Phase III clinical trials for ivonescimab in NSCLC, HARMONi-A and HARMONi-2.
HARMONi-A was a Phase III clinical trial which evaluated ivonescimab combined with chemotherapy compared to placebo plus chemotherapy in patients with EGFR-mutated, locally advanced or metastatic non-squamous NSCLC who have progressed after treatment with an EGFR TKI.
HARMONi-2 is a Phase III clinical trial evaluating monotherapy ivonescimab against monotherapy pembrolizumab in patients with locally advanced or metastatic NSCLC whose tumors have positive PD-L1 expression (PD-L1 TPS >1%).
Ivonescimab is an investigational therapy that is not approved by any regulatory authority in Summit’s license territories, including the United States and Europe. Ivonescimab was approved for marketing authorization in China in May 2024.