Highest Non-severely Toxic Dose Research Articles

Preclinical Profile of BYON3521 Predicts an Effective and Safe MET Antibody-Drug Conjugate.

MET, the cell-surface receptor for the hepatocyte growth factor/scatter factor, which is widely overexpressed in various solid cancer types, is an attractive target for the development of antibody-based therapeutics. BYON3521 is a novel site-specifically conjugated duocarmycin-based antibody-drug conjugate (ADC), comprising a humanized cysteine-engineered IgG1 monoclonal antibody with low pmol/L binding affinity towards both human and cynomolgus MET. In vitro studies showed that BYON3521 internalizes efficiently upon MET binding and induces both target- and bystander-mediated cell killing. BYON3521 showed good potency and full efficacy in MET-amplified and high MET-expressing cancer cell lines; in moderate and low MET-expressing cancer cell lines good potencies and partial efficacy were observed. In mouse xenograft models, BYON3521 showed significant antitumor activity upon single-dose administration in multiple non-MET-amplified tumor types with low, moderate, and high MET expression, including complete tumor remissions in models with moderate MET expression. In the repeat-dose Good Laboratory Practice (GLP) safety assessment in cynomolgus monkeys, BYON3521 was well tolerated and based on the observed toxicities and their reversibility, the highest non-severely toxic dose was set at 15 mg/kg. A human pharmacokinetics (PK) model was derived from the PK data from the cynomolgus safety assessments, and the minimal efficacious dose in humans is estimated to be in the range of 3 to 4 mg/kg. In all, our nonclinical data suggests that BYON3521 is a safe ADC with potential for clinical benefit in patients. A first-in-human dose-escalation study is currently ongoing to determine the maximum tolerated dose and recommended dose for expansion (NCT05323045).

Abstract 6332: A humanized anti-cd40 antibody with anti-tumor pharmacological activity and cynomolgus monkey safety

Abstract LNF1901 is a humanized CD40 agonistic antibody. LNF1901 can bind to CD40 protein of human(EC50=23.6ng/mL) and monkey(EC50=23.5ng/mL), but cannot bind to CD40 protein of rat and mouse. LNF1901 had strong activation effect on DC cells(EC50=0.04ug/mL) and had strong ADCC and CDC effects. AT a dose of 20mg/kg, the TGITW of LNF1901 was 59.9% in Female NPG mice were inoculated with Raji/CIK/DC subcutaneous transplanted tumor model. Following intravenous infusion of LNF1901 at doses of 6, 30, or 150 mg/kg to cynomolgus monkeys weekly for 4 weeks, the highest non-severely toxic dose (HNSTD) was considered to be 150 mg/kg.LNF1901 had demonstrated manageable safety and promising antitumor activity in vivo and in vitro tests. Citation Format: Zhenyu Li, Lili Zhao, Guimin Zhang, Bin Li, Zhong Liu, Guangyan Li, Zhongsong Zhu. A humanized anti-cd40 antibody with anti-tumor pharmacological activity and cynomolgus monkey safety [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6332.

Abstract 1884: DB-1310, a novel Her3 targeting antibody-drug conjugate, exhibits therapeutic efficacy for solid tumors

Abstract Background: HER3 (ErbB3), a member of the human epidermal growth factor receptor family, is frequently overexpressed in various cancers. Its high expression is associated with poor prognosis in several solid tumors. Many anti-Her3 antibodies have been developed for cancer therapy. To date, only patritumab deruxtecan (U3-1402) showed clinical efficacy in both NSCLC and breast cancer among all Her3-targeting therapies. DB-1310 is a HER3 ADC composed of a novel humanized anti-Her3 immunoglobulin G1 (IgG1) monoclonal antibody, covalently linked to a proprietary DNA topoisomerase I inhibitor payload via a maleimide tetrapeptide-based cleavable linker with a drug antibody ratio (DAR) of approximately eight. In the present study, we aim to evaluate the efficacy and safety of DB-1310 in preclinical models. Methods: The binding of DB-1310 to Her3 and other HER families was measured by ELISA and SPR. The competition of binding epitope for DB-1310 and patritumab was tested by FACS. The sensitivity of breast cancer and lung cancer cell lines to DB-1310 was evaluated by in vitro cell killing assay. In vivo growth inhibition study evaluated the sensitivity of DB-1310 to Her3-positive breast cancer and lung cancer xenograft models. In addition, the efficacy of DB-1310 was compared to that of patritumab deruxtecan in tumor xenograft models. The pharmacokinetics and safety profile were also measured in cynomolgus monkey. Results: In this study, DB-1310 showed high affinity to both Human and Cyno Her3 without cross reacting with Her2, Her4 or EGFR. DB-1310 binds Her3 using a different epitope from patritumab. DB-1310 has high internalization capability and translocates into lysosomes after internalization. In vitro, DB-1310 exhibited cytotoxicity in a panel of Her3- expression human breast cancer and lung cancer cell lines. It also showed dose-dependent antitumor killing activity in a HER3-positive breast cancer HCC1569 xenograft model and a lung cancer NCI-H441 xenograft model. Tumor regression was observed in a NSCLC patient-derived xenograft model with EGFR mutation under DB-1310 treatment. Moreover, DB-1310 showed stronger tumor growth inhibition than that of patritumab deruxtecan at the same dose. The systemic exposure AUC0-last and Cmax of DB-1310 and total antibody increased dose proportionally from 1 mg/kg to 10 mg/kg with low released payload in serum. The DB-1310 also showed good safety profile with highest non-severely toxic dose (HNSTD) above 30mg/kg. Conclusions: DB-1310 exhibited its efficacy in tumor models both in vitro and in vivo. These studies suggest that DB-1310 as a novel HER3-targeting ADC showed antitumor efficacy for HER3 positive tumors with good safety profile. Citation Format: Xi Li, Jun Yao, Chen Qu, Luo Lan, Bing Li, Yu Zhang, Rong Shi, Haiqing Hua, Yang Qiu. DB-1310, a novel Her3 targeting antibody-drug conjugate, exhibits therapeutic efficacy for solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1884.

Abstract P4-01-12: BAT8006, a novel FRα ADC with strong bystander effect, for the treatment of advanced solid tumor

Abstract FRα is overexpressed in a number of cancers, including ovarian, breast, lung cancer, and endometrial carcinoma, yet limited expression in normal tissue. Efficacy of anti-FRα ADC have been demonstrated in clinical trials for high FRα expression ovarian cancer. These results validate FRα as a viable target for cancer treatment. We have developed a novel FRα ADC with strong bystander killing effect, BAT8006, which consists of a high-affinity antibody, an enzymatically cleavable linker and a topoisomerase I inhibitor as the payload, with DAR of 8. BAT8006 shows high affinity for the FRα antigen (KD < 0.5 nM) and FRα-expressing tumor cells. Upon binding to FRα on cell surface, BAT8006 internalizes effectively and traffics to the lysosome where payload is proteolytically released. BAT8006 demonstrated potent in vitro cell growth inhibitory activity to FRα-positive cells with IC50 values of ~ 1 nM. In an in vitro bystander killing assay, proliferation of FRα-negative cells was potently inhibited by addition of culture medium of BAT8006-treated FRα-positive cells, but not that of BAT8006-treated FRα-negative cells, indicating the bystander killing effect of the released payload in the culture medium. Less than 0.03% of the payload was released from BAT8006 when incubated with human or monkey plasma for 4 days in 37oC, suggesting the stability of BAT8006 in blood circulation. BAT8006 led to potent and dose-dependent tumor regression in patient-derived xenograft (PDX) model of SCLC. Furthermore, single dose of 2.5 mg/kg of BAT8006 showed complete eradication of tumor in choriocarcinoma JeG-3 xenograft mice model. In PDX of ovarian cancer, 2.5 mg/kg of BAT8006 (DAR8) demonstrated superior tumor inhibition activity than 5 mg/kg of BAT8006 with DAR4, suggesting the high DAR approach of BAT8006 would be more effective. In addition, BAT8006 showed favorable pharmacokinetic and safety profiles in cynomolgus monkeys with the highest non-severely toxic dose (HNSTD) of 30 mg/kg when dosed once every three weeks for 3 times. Together these results indicate that BAT8006 could potentially provide a therapeutic benefit to treat FRα-positive tumors including breast cancer in clinical trial. Citation Format: siqi mai, xingxing Mei, weijia Tang, Xin Zhou, Xuekang qi, Zhi Zhong, Shuoxu Li, Jianjun fan, Jirong Gan, Binghua Tan, Yao Qi, Yanling Guo, Shengfeng li, Jin-Chen Yu. BAT8006, a novel FRα ADC with strong bystander effect, for the treatment of advanced solid tumor [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-12.

Abstract P4-01-32: BAT8008, a novel Trop-2 ADC with strong bystander effect, for the treatment of Trop-2 positive cancer

Abstract Trophoblast cell surface antigen 2 (Trop-2) is overexpressed on many epithelial carcinomas, yet is expressed at much lower level on normal tissue. Elevated expression of TROP-2 is often associated with tumor invasion/aggression, progression, and metastasis. Efficacy of anti-TROP2 ADC have been demonstrated in clinical trials for both TNBC (triple negative breast cancer) and HR+/HER2- breast cancer. We have developed a novel Trop-2 ADC with strong bystander killing effect, BAT8008, which consists of an enzymatically cleavable linker and a topoisomerase I inhibitor as the payload, with DAR of 6. BAT8008 demonstrated potent in vitro cell growth inhibitory activity to Trop2-positive cells with IC50 values of < 1 nM. In an in vitro bystander killing assay, proliferation of Trop-2-negative cells was potently inhibited by addition/transfer of culture medium of BAT8008-treated Trop-2-positive cells, but not that of BAT8008-treated Trop-2-negative cells, indicating the bystander killing effect of the released payload in the culture medium. Less than 0.1% of the payload was released from BAT8008 when incubated with human or monkey plasma for 7 days in 37°C, suggesting the stability of BAT8008 in blood circulation. Single dose of BAT8008 at 1 and 2.5 mg/kg could inhibit 73% and 81% tumor growth in the Trop-2-positive MDA-MB-468 and MX-1 xenograft mice model, respectively. BAT8008 also demonstrated superior tumor inhibition activity than a modified ADC using Daiichi’s ADC technology or Trodelvy in a pancreatic BxPC-3 xenograft mice model. In addition, BAT8008 showed favorable pharmacokinetic and safety profiles in cynomolgus monkeys with the highest non-severely toxic dose (HNSTD) of at least 25 mg/kg when dosed once every two weeks for 3 times. Together these results indicate that BAT8008 could potentially provide a therapeutic benefit to treat TROP2-positive breast cancers in clinical trial. Citation Format: Xingxing Mei, Weijia Tang, Xin Zhou, Xuekang Qi, Siqi Mai, Zhi Zhong, Shuoxu Li, Jianjun Fan, Jirong Gan, Binghua Tan, Yao Qi, Yanling Guo, Jin-Chen Yu, Shengfeng Li. BAT8008, a novel Trop-2 ADC with strong bystander effect, for the treatment of Trop-2 positive cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-32.

Toxicologic Pathology Forum: Opinion on Approaches for Reporting Toxic and Adverse Dose Levels in Nonclinical Toxicology Studies Supporting the Development of Anticancer Pharmaceuticals.

The advancement of an investigational new drug in humans is a significant developmental milestone. In first-in-human (FIH)-enabling toxicology studies, the highest dose without a test article-related adverse effect (no-observed-adverse-effect-level [NOAEL]) serves as the basis for deriving a safe FIH starting dose. For anticancer pharmaceuticals, the FIH dose may be calculated using the highest non-severely toxic dose (HNSTD) in nonrodent models or the dose severely toxic to 10% (STD10) in rodents. Given the practice of reporting the NOAEL, but the lack of regulatory requirements to do so for anticancer pharmaceuticals, we conducted an informal survey of 20 companies to answer the question "How is our industry reporting toxic/adverse dose levels in FIH-enabling toxicology studies for anticancer indications?" The data indicated 4 reporting approaches, each providing a path to regulatory acceptance. Within the integrated toxicology study report, 45% of respondents report the HNSTD/STD10, 25% report the NOAEL, 20% report both the HNSTD/STD10 and NOAEL, and 10% do not define either, reserving definitions for regulatory submissions. One reporting approach may be preferred over another for reasons including consistency across indications, repurposing pharmaceuticals, regulatory feedback, or simplicity. The reporting approach should be defined in advance of study initiation, and the pathologist should provide context to support the chosen approach.

A CD79b Targeting ADC with Superior Anti-Tumor Activity and Safety Resulting in Significantly Improved Therapeutic Index (TI): Safe and Efficacious CD79b ADC

The Araris' site-specific and 1-step enzymatic linker conjugation technology aims at generating safe and highly potent ADCs without the need for antibody engineering prior to linker-payload conjugation. We developed a very stable anti-CD79b-MMAE ADC (ARC-02) with this technology showing a higher therapeutic index (TI) compared to the approved ADC polatuzumab-vedotin (Polivy®) in different preclinical models. Therefore, ARC-02 is considered a promising next generation treatment alternative for patients suffering from Non-Hodgkin lymphoma (NHL). Using native polatuzumab as the targeting antibody and monomethyl auristatin E (MMAE) as payload, we generated within 24 hours the highly homogeneous and pure ARC-02 development candidate with a well-defined drug-to-antibody ratio (DAR) of 1.9 and with high purity (monomer content > 98%). ARC-02 is highly stable under stressed conditions at elevated temperatures and maintains the FcyR/FcRn-binding properties of the parental mAb. In-vitro ARC-02 demonstrated potent cytotoxicity in four different NHL cell lines tested so far with similar potency (EC50 values) compared to the approved Polivy® ADC despite of the lower toxin load of ARC-02 (DAR of 1.9) compared to Polivy® (DAR of 3.5). ARC-02 clearly differentiates from Polivy® by extraordinary stability in mouse, cynomolgus monkey and human sera exemplified by the absence of payload deconjugation or linker cleavage under physiological conditions (at 37°C) and long-term incubation (>2 weeks). Exceptional stability could also be confirmed in vivo in pharmacokinetic studies in mice, rats and cynomolgus monkeys demonstrating an antibody-like exposure profile comparable to the unmodified polatuzumab parental antibody without premature toxin deconjugation in the circulation resulting in improved pharmacokinetics of ARC-02 compared to Polivy® (half-life in mice 10 days for ARC-02 vs 5 days for Polivy®). Despite the excellent stability of ARC-02 in vitro and in vivo, the MMAE toxin is still efficiently released from ARC-02 in lysosomal human Cathepsin B cleavage or human liver-lysosome release assays which is providing the foundation for the observed robust anti-tumor activity in vivo: ARC-02 was compared head-to-head to Polivy® in two different CD79b-expressing established tumor models in vivo (Granta-519 and Ramos). Single dose treatment of ARC-02 at very low payload doses induced effective and long-lasting anti-tumor responses with complete tumor eradication achieved at about half of the Polivy® payload dose in both NHL established tumor models. Based on these in vivo efficacy experiments, the minimal effective dose (MED) of ARC-02 that is still inducing eradication of established tumors is determined to be as low as 10 μg/kg based on the MMAE payload dose or 1 mg/kg based on the total ADC dose. Finally, the highest non-severely toxic dose (HNSTD) of ARC-02 in repeat dose toxicology studies was determined to be ≥30 mg/kg and ≥24 mg/kg in rats and cynomolgus monkeys, respectively, which is substantially higher than the HNSTD reported for Polivy® (i.e. 10 mg/kg in the rat and 3 mg/kg in the cynomolgus monkey as described in the Polivy® Biologic License Application). Therefore, the tolerability in rodents and non-human primates is at least 3 and 8 times higher when compared to historical safety data of Polivy®. Using the HNSTD derived from repeat dose non-human primate toxicity study (24 mg/kg) and the MED calculated from single dose rodent efficacy studies (1 mg/kg) an impressive TI of 24 can be calculated for ARC-02 which is substantially higher than the TI of Polivy®. These encouraging results obtained so far indicate that ARC-02 a) has very favorable biophysical properties, b) shows a consistent and highly defined DAR, c) is highly stable in vitro and in vivo, d) is highly potent and efficacious in multiple tumor models and e) has improved tolerability in rodents and non-human primates and f) shows an impressive improvement in TI and ultimately warrant further development of ARC-02.

252 (PB032) - DB-1303, a HER2-targeting ADC with a novel DNA topoisomerase I inhibitor, demonstrates a promising safety profile and anti-tumor efficacy with differentiation from DS-8201a

Background: DB-1303 is a novel antibody-drug conjugate comprised of trastuzumab biosimilar, enzymatically cleavable peptide-linker, and a proprietary topoisomerase I inhibitor P1003. It is designed to have high plasma stability, low free payload in circulation and wide therapeutic index. Herein, we describe the preclinical profile of DB-1303, including efficacy, pharmacokinetics, and safety. Material and Methods: In vitro cell growth inhibition and in vivo antitumor activities of DB-1303 were evaluated in several Her2-low tumor cell lines and xenograft models. Tumor-bearing mice were used to assess pharmacokinetic and pharmacodynamic characteristic of DB-1303. The mechanism of action for the efficacy was also evaluated. Plasma stability of DB-1303 was determined with rat, monkey, and human plasma. Pharmacokinetic and safety profiles of DB-1303 were evaluated in cynomolgus monkeys. Results: In vitro, DB-1303 selectively binds to and is endocytosed into the lysosome of HER2-positive cells. DB-1303 causes G2/M cell cycle arrest, induces DNA damage, and inhibits cell proliferation in HER2-expressing cells. Importantly, DB-1303 showed inhibitory activity to Her2 low-expressing CAPAN-1 (pancreatic cancer) and Ishikawa (endometrial cancer) cell lines. Under a coculture condition of HER2-positive KPL-4 cells and HER2-negative MDA-MB-468 cells in vitro, DB-1314 inhibited the proliferation of both cells, demonstrating its bystander effect. In vivo, DB-1303 induced dose-dependent tumor growth inhibition and tumor regression in T-DM1-resistant JIMT-1 xenograft model, HER2 low-expressing Ishikawa xenograft and two HER2-low breast cancer PDX models. A single dosing of DB-1303 in NCI-N87 tumor-bearing mice induced significant DNA damage in tumors, and the Cmax of payload in tumor tissues was about 45-fold higher than that in peripheral blood. Pharmacokinetics and safety profiles of DB-1303 were favorable and the highest non-severely toxic dose was 80 mg/kg in cynomolgus monkey study with Q3W dosing of 3 repeated doses. It’s worth noting that, unlike DS-8201a, no interstitial pneumonia was observed in monkeys during the dosing period and recovery period. The payload P1003 poses very low risk of drug-drug interaction. Following administration of DB-1303, systemic P1003 exposure was low and P1003 was cleared rapidly. Conclusions: DB-1303 exhibited potent antitumor activity in both HER2 positive and HER2 low tumor models with a wide therapeutic window. The stable linker in circulation and fast clearance of P1003 may contribute to the superior safety profile of DB-1303. These studies suggest the potential of DB-1303 to address unmet medical needs in HER2 expressing cancers, especially in HER2 low cancers. At the time of presentation, a first-in-human phase 1/2 study in patients with advanced solid tumors is in progress (NCT05150691). No conflict of interest.

253 (PB033) - The Trop-2-targeting antibody drug conjugate DB-1305 has higher antitumor activity and a potentially better safety profile compared with DS-1062

Background: Trop-2 is a well validated oncology therapeutic target. DB-1305 is an antibody drug conjugate designed by conjugating an anti-Trop-2 antibody with a novel topoisomerase I inhibitor P1021 via an enzymatically cleavable tetrapeptide linker. Material and Methods: To characterize DB-1305 and the payload P1021, thorough studies were performed including in vitro functional assays, in vivo efficacy and PK/PD studies with murine CDX models, as well as PK/TK and GLP toxicity studies in monkeys and rats. Results: The results show that in vitro, DB-1305 selectively bound to Trop-2-positive cells and was endocytosed into their lysosomes. DB-1305 led to Trop-2-dependent cytotoxicity in Trop-2-expressing cells but not Trop-2-negative cells in a concentration-dependent manner. DB-1305 demonstrated tumor cell proliferation inhibition activities comparable to or stronger than DS-1062 produced in-house, as well as intriguingly displayed a stronger bystander killing effect. in vivo, DB-1305 showed strong anti-tumor activity in mouse models of MDA-MB-468, COLO205 and DMS-53, with significantly higher efficacy compared with DS-1062. In Trop-2 negative SHP77 model, DB-1305 did not suppress tumor growth, indicating the dependence of DB-1305 activity on Trop-2 expression. The PK/PD study performed by treatment of DB-1305 in the MDA-MB-468 model demonstrated substantially increased ratios of P1021 exposure (AUC) to the exposure of DB-1305-total antibody or DB-1305-ADC in the tumor than in serum, suggesting that P1021 is effectively released in the tumor. The pharmacokinetics parameters of DB-1305 (total antibody, ADC, and released payload) were obtained from the PK/TK studies in monkeys. The PK/TK profile of P1021 was assessed in rats in addition to the PK/TK study of DB-1305 in monkeys. The exposure levels of DB-1305 and P1021 had no obvious gender difference and no apparent accumulation in monkeys and rats. The systemic exposure AUC0-last and Cmax of ADC showed similar values to those of total antibody, and both parameters were increased approximately dose proportionally from 1 mg/kg to 10 mg/kg. Particularly, in monkeys, the peak concentration of P1021 in the DB-1305 10 mg/kg group was reduced to 1/171 compared with the P1021 0.14 mg/kg (equivalent to the molar mass of P1021 in 10 mg/kg DB-1305), while the t1/2 was prolonged from 0.651 h to 194 h. DB-1305 was well tolerated in the GLP toxicity studies in Cynomolgus monkeys with the highest non-severely toxic dose (HNSTD) of 80 mg/kg, which is significantly higher than HNSTD of 30 mg/kg for DS-1062. Conclusions: Taken together, this study has demonstrated higher efficacy and a potentially better safety profile of DB-1305 compared with DS-1062, supporting further clinical development of DB-1305 and indicating the great potential of DB-1305 in the treatment of Trop-2-positive cancers. No conflict of interest.

Abstract 1751: Developing a next generation antibody drug conjugate for treatment of gastrointestinal cancers

Abstract Background: Gastrointestinal cancers (GI) are among the most common cancers worldwide. Current treatment options rely on a chemotherapy backbone combined with targeted antibody therapies, but the prognosis generally remains poor. Iksuda has developed a next-generation Antibody Drug Conjugate (ADC) targeting a cancer-specific carbohydrate antigen (CanAg) which is highly overexpressed in GI cancers but has no expression on normal tissues. This CanAg-targeting ADC is comprised of a proprietary PBD prodrug coupled to an anti-CanAg antibody using PermaLink conjugation technology. The PBD prodrug is designed with a tumor-selective trigger to attenuate its potency before entry of the ADC into the target cancer cells. PermaLink conjugation chemistry ensures conjugate stability. Here, the potential of this anti-CanAg ADC was explored in preclinical models as a proof of concept for targeting GI cancers. Methods: The ADC is composed of a PBD prodrug conjugated to an anti-CanAg antibody through PermaLink to generate conjugate with a drug to antibody ratio of approximately 2. This CanAg-targeting ADC was evaluated in vitro in the CanAg-expressing Colo205 cancer cell line. In vivo efficacy studies were conducted in SCID mice with CanAg-expressing human cancer xenografts representing colorectal (Colo 205), gastric (N87) and pancreatic cancers (BxPC3). An exploratory toxicology study was conducted in cynomolgus monkeys. Results: The CanAg-targeting ADC showed highly potent, specific activity in the Colo205 colorectal cancer cell line with IC50 values in the pM range. A single administration of anti-CanAg ADC in CanAg-positive GI xenograft models showed significant dose-dependent antitumor activity and induced complete tumor regressions with no observable toxicity. In the gastric cancer model, the anti-CanAg ADC gave a complete response by day 36 when dosed at 0.3 mg/kg, and 1 and 3 mg/kg doses exhibited long-lasting tumor regression. In the pancreatic cancer model, administration of anti-CanAg ADC at 0.3 mg/kg induced 76% tumor growth inhibition (TGI) on day 21, and at 1 mg/kg, and 3 mg/kg showed complete tumor regression by day 40 with no subsequent tumor recurrence for the 3mg/kg dose. In colorectal cancer, the anti-CanAg ADC exhibited 58% and 98% TGI with 0.3 mg/kg and 1 mg/kg doses respectively, and with the 3 mg/kg dose regressed tumor with no recurrence. The anti-CanAg ADC was well tolerated in cynomolgus monkeys with 1 mg/kg defined as the highest non-severely toxic dose (HNSTD). Conclusions: This anti-CanAg ADC has shown favorable preclinical anti-tumor activity in gastrointestinal cancers. Our findings support the clinical development of the anti-CanAg ADC for the treatment of GI cancers. Citation Format: Justyna H. Mysliwy, Adam Lodge, Daniel Williamson, Jenny Thirlway, Jutta Deckert, Robert J. Lutz. Developing a next generation antibody drug conjugate for treatment of gastrointestinal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1751.

Abstract 2910: A CD79b targeting ADC with superior anti-tumor activity and therapeutic index

Abstract The Araris’ site-specific and 1-step linker conjugation technology aims at generating safe and highly potent ADCs without the need for antibody engineering prior to linker-payload conjugation. We developed a very stable anti-CD79b-MMAE ADC with this technology showing a higher therapeutic index compared to polatuzumab-vedotin in preclinical models. Our ADC may represent a safe and efficacious alternative for the treatment of patients with diffuse-large B-cell lymphoma (DLBCL).Using native polatuzumab (non-engineered, same antibody sequence as present in approved polatuzumab-vedotin) as the targeting antibody and monomethyl auristatin E (MMAE) as payload, we generated within 24hours highly homogeneous and pure ADCs with a well-defined drug-to-antibody ratio (DAR) of 1.9, with a &gt 98% monomer content. The ADC is highly stable under stressed conditions at elevated temperatures and maintains the FcyR/FcRn-binding properties of the parental mAb. In in-vitro assays our ADC demonstrated potent cytotoxicity in four tested cell-lines, similar to the approved polatuzumab-vedotin (Polivy®). Moreover, our anti-CD79b ADC (ARADC) is highly stable in mouse, cynomolgus and human sera exemplified by the absence of payload deconjugation or linker cleavage. Though highly stable, the ADC is still efficiently released by lysosomal human Cathepsin B cleavage or human liver-lysosome enzymes. Most importantly, the resulting ADC is extremely stable in circulation as shown in pharmacokinetic studies in mice and rats demonstrating an antibody-like exposure profile comparable to the unmodified polatuzumab antibody and twice as long as the approved polatuzumab-vedotin (half-life 10d vs 5d).Most importantly, the in vivo efficacy of ARADC (DAR 1.9) was compared with approved polatuzumab-vedotin (DAR 3.5) in two CD79b-expressing tumor models: Granta-519 and Ramos. ARADC provided equal tumor growth inhibition and survival at about half the payload dose relative to polatuzumab-vedotin in both models. At approximately equal payload doses, ARADC treatment led to greater antitumor effects and a considerably longer survival advantage over polatuzumab-vedotin in both models. Finally, the highest non-severely toxic dose (HNSTD) of ARADC was determined at 30mg/kg in a 4-week repeat dose toxicology study in rats. This observation, together with the high anti-tumor potency at low dose - the minimal effective dose (MED), results in an overall 4-6-fold increased therapeutic index (TI).These encouraging results obtained so far indicate that ARADC a) has very favorable biophysical properties, b) shows a clearly defined drug-to-antibody ratio, c) is highly stable in vitro and in vivo, d) is highly potent and efficacious in multiple tumor models and e) showed an improvement in TI by a factor of 4-6 and ultimately warrant further development of ARADC. Citation Format: Isabella Attinger-Toller, Philipp Probst, Romain Bertrand, Ramona Stark, Roger Santimaria, Emma Renard, Rachael Fay, Dragan Grabulovski, Bernd Schlereth, Philipp René Spycher. A CD79b targeting ADC with superior anti-tumor activity and therapeutic index [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2910.

D3S-001, a highly potent, selective, and differentiated covalent inhibitor of KRAS G12C: Human dose prediction and first‐in‐human (FIH) trial design.

e15087 Background: Effective inhibition of G12C mutated KRAS is believed to be critical for anti-tumor efficacy in KRAS-driven cancers. D3S-001 is a potent and highly differentiated KRAS G12C inhibitor, which demonstrates rapid and near complete target inhibition and strong anti-tumor activity in preclinical cell line and animal models [Preclinical characterization of D3S-001, a highly potent, selective, and differentiated covalent inhibitor of KRAS G12C, ASCO 2022 Abstract #378099]. The current study utilizes pharmacokinetic (PK) modeling to predict the extent of KRAS G12C target inhibition at the proposed clinical dose range. Methods: Allometric scaling and non-linear fixed effect modeling were used to predict human PK profiles from DMPK data in animals. Human in vivo target inhibition was calculated based on human PK predictions, free drug fraction and results from in vitro target engagement assay. A First-in-Human (FIH) study was designed to investigate D3S-001 monotherapy in subjects with advanced solid tumors having a KRAS G12C mutation. Six dose escalation cohorts will be investigated, starting from 50mg QD. Results: Based on a GLP toxicology study in dogs, the highest non-severely toxic dose (HNSTD) was determined to be 20 mg/kg/day. Per ICH S9, a 20 mg/kg/day dose in dog supports a FIH starting dose of 110 mg. To ensure an additional safety margin, a lower starting dose of 50 mg was proposed. At 50 mg QD, the predicted human exposure (Cmax 60 nM, Caverage 49 nM, Ctrough 31 nM) is expected to achieve ̃70% target inhibition at 2 hours after dosing. In NCI-H358 mouse xenograft model, this exposure is associated with 94% tumor growth inhibition (TGI). Safety margins based on Cmax and AUC comparing to dog HNSTD are 17-fold and 9-fold, respectively. At 100 mg QD, the predicted human exposure (Cmax 120 nM, Caverage 98 nM, Ctrough 63 nM) is expected to achieve ̃95% target inhibition. This exposure is associated with tumor regression of 72% in the NCI-H358 mouse xenograft model. At dose levels higher than 100 mg QD, predicted human exposures are expected to consistently achieve >95% target inhibition starting 1 hour after dosing. These exposures are associated with deeper levels of tumor regression of 97%. Moreover, even at 400 mg QD, predicted human plasma concentrations are still below dog plasma concentration of 443 nM, Caverage at HNSTD. Conclusions: D3S-001 is predicted to achieve rapid and consistently efficacious KRAS G12C target inhibition in humans at proposed clinical dose range. This high degree of KRAS G12C inhibition over the dosing interval may translate into greater clinical benefit to patients with KRAS G12C mutations comparing with other clinical-stage KRAS G12C inhibitors. Clinical data from the FIH study will be evaluated and compared to preclinical predictions.

TIP: A phase I/II study of MGTA-117, an anti-CD117 antibody-drug conjugate, in patients with adult acute myeloid leukemia (AML) and myelodysplasia with excess blasts (MDS-EB).

TPS3156 Background: Hematopoietic stem cell transplantation (HSCT) is used with curative intent for AML and MDS-EB. MGTA-117 is a novel Ab-drug conjugate (ADC) in development for conditioning prior to HSCT. MGTA-117 selectively targets CD117 (c-Kit) with a human monoclonal Ab to CD117 conjugated to an amanitin payload that depletes CD117-expressing cells by inhibiting RNA polymerase II. Human hematopoietic stem cells and AML tumor cells express high levels of CD117, and MGTA-117 potently depletes these target cells, with an IC50 of <10pM in vitro. MGTA-117 has demonstrated in vitro and in vivo stability, confirming its characterization as a highly potent and selective agent. In a primate GLP toxicology study, MGTA-117 maximally depleted bone marrow stem cells at a dose not associated with evidence of toxicity in other tissues. Dose-dependent reduction of peripheral reticulocytes, produced from CD117+ erythroid precursors in the bone marrow, was an early and time sensitive biomarker of bone marrow CD117+ cell depletion. Higher doses were associated with the elevation of transaminases and histopathology that were asymptomatic and transient. Highest Non- Severely Toxic Dose (HNSTD) was used to establish the starting dose in this First-in-Human study. Based upon dose exposure and allometric scaling, it is expected that the clinical exposures after a 0.02 mg/kg dose in the first human cohort will provide an optimal > 100-fold safety margin over exposures observed after the 0.3 mg/kg dose that was the HNSTD in the primate GLP toxicology study. Methods: This phase I/II, multicenter, open-label, dose-escalation study will investigate the safety, tolerability, PK profile, PD activity, and blast depletion activity of MGTA 117 given intravenously as a single dose in adults with R/R AML or MDS-EB. Patients must be 18-75 yrs, have a WHO-defined diagnosis of CD117+ R/R AML or MDS-EB with ≥5% marrow myeloblasts. Patients must have ECOG PS ≤2, and adequate hepatic, renal, and cardiac function. The primary objective is to establish a minimum safe and biologically effective (MSBE) dose of MGTA-117 in R/R AML and MDS-EB patients based on safety and CD117 receptor occupancy (RO) in circulating leukemic blasts after dosing. The observation period for dose limiting toxicities is 21 days. Patients will be followed for changes in reticulocyte, neutrophil, and platelet counts in PB and percent change from baseline in leukemic blasts or stem/progenitor cells in PB and/or BM. CD117 receptor occupancy by MGTA-117 will be measured and MSBE dose will be based on safety and receptor occupancy. The study is designed with the possibility that subjects would proceed to HSCT >28 days after MGTA-117 administration, if eligible per the local transplant practices. Clinical trial information: NCT05223699.

Abstract P2-13-33: Preclinical development of DHES0815A: A HER2-directed antibody-drug conjugate comprised of a reduced potency PBD dimer linked to a domain I binding HER2 antibody

Abstract Background: Many HER2-directed antibody-drug conjugates (ADCs) in early development employ trastuzumab linked to tubulin binding agents as the cytotoxic drug. DHES0815A is an ADC consisting of a THIOMABTM humanized IgG1 anti-HER2 monoclonal antibody (hu7C2), which binds domain 1 of the HER2 ECD, conjugated via a disulfide linker to PBD-monoamide (MA), a DNA mono-alkylating agent. The reduced potency of the PBD-MA payload compared to PBD dimers and the stability of the conjugation site and linker were designed to improve tolerability, whereas the binding of hu7C2 to a HER2 epitope distinct from trastuzumab and pertuzumab allows combination with existing HER2 therapies. . Methods: Modifications at one imine in the PBD (pyrrolobenzodiazepine) dimer produced mono-alkylating PBDs that were assessed for DNA binding, permeability and cell potency. Each modified PBD was conjugated to hu7C2 LC K149C via a disulfide linker and assessed in HER2-positive models in vitro and in vivo. Safety studies were performed in female and male cynomolgus monkey treated every 3 weeks X 5, with a 7-week follow-up. Assessments included hematology, clinical chemistry, anti-drug antibody, standard clinical, neurological and ophthalmic exams and histopathology. Results: Our goal was design of a reduced potency PBD dimer ADC to achieve dosing in the linear PK range for optimal exposure, efficacy and safety. PBD dimers contain 2 reactive imines that bis-alkylate and crosslink DNA. Mono-alkylating PBD dimers were assessed in DNA binding, potency and permeability assays to select the optimal mono-alkylator, PBD-MA, for further investigation. hu7C2-disulfide-PBD-MA, or DHES0815A, was potent across HER2-positive breast and gastric cancer models in vitro and in vivo, with little effect on HER2-negative tumors or normal primary cells in vitro. DHES0815A was more potent than T-DM1 in HER2-positive and HER2-low breast and gastric cancer PDX models and demonstrated combination activity with standard of care agents T-DM1 or docetaxel. Mechanistically, treatment of HER2-positive cells with DHES0815A resulted in late S-phase cell cycle arrest; induction of DNA damage markers γH2AX, phospho-p53, phospho-CHK2, induction of apoptosis, and bystander activity. Pharmacokinetic analysis showed dose-proportional PK, with linear biphasic PK >/= 4mg/kg in cynomolgus monkey. Safety studies in cynomolgus monkey treated with 4, 8 or 12 mg/kg demonstrated that findings were non-adverse, monitorable and manageable. All doses were tolerated with few clinical observations and minimal to mild clinical pathology changes. Target organs were skin, bone marrow, lung and eye. The HNSTD (highest non-severely toxic dose) was 12 mg/kg. This dose enabled a starting dose of 0.6 mg/kg for phase 1 testing. Conclusions: DHES0815A is a HER2-directed ADC comprised of a domain I binding antibody linked to a reduced potency PBD dimer, PBD-MA, via a reducible disulfide linker. The antibody does not interfere with trastuzumab or pertuzumab binding, allowing combination with existing HER2 therapies. The reduced potency payload allows dosing in the linear PK range, supporting our hypothesis. DHES0815A demonstrated dose-dependent anti-tumor efficacy in multiple HER2+ breast and gastric cancer models, and showed efficacy in HER2-low models, where T-DM1 was inactive. Enhanced anti-tumor activity was observed combining DHES0815A with T-DM1, trastuzumab/pertuzumab or docetaxel. Studies in cynomolgus monkey demonstrated a safety profile compatible with initiating a phase 1 clinical trial. The phase 1 data will be presented in a separate presentation. Citation Format: Gail Lewis Phillips, Guangmin Li, Jun Guo, Shang-Fan Yu, Genee Lee, Donglu Zhang, Peter Dragovich, Thomas Pillow, Binqing Wei, M. Violet Lee, Ola Saad, Shab Masih, Douglas Leipold, Lisa Crocker, Melissa Schutten. Preclinical development of DHES0815A: A HER2-directed antibody-drug conjugate comprised of a reduced potency PBD dimer linked to a domain I binding HER2 antibody [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-33.

Abstract 1347: The CAPAC Platform maximizes therapeutic benefit and reduces systemic cytotoxic exposure in small and large animals

Abstract The Click Activated Protodrugs Against Cancer (CAPACTM) platform aims to beat cancer without poisoning the body by activating powerful cancer therapies at the tumor site(s). CAPAC's mechanism of activation is based on click chemistry and is therefore agnostic to tumor characteristics, biomarker expression or other biological factors that vary across patients. This allows the CAPAC platform to be readily applicable to diverse tumor types. We describe the safety, pharmacokinetic and therapeutic benefits of SQ3370, the lead candidate of the CAPAC Platform, in small and large animals. SQ3370 consists of 2 components, SQL70 biopolymer and SQP33 protodrug. First, SQL70, a tetrazine-modified sodium hyaluronate biopolymer, is injected at the tumor site. Then, SQP33, a trans-cyclooctene (TCO)-modified protodrug of Doxorubicin (Dox) is given by IV infusion as 5 daily doses. The SQP33 protodrug has attenuated toxicity and is converted to active Dox by the SQL70 biopolymer at the tumor site through a highly efficient covalent reaction between tetrazine and TCO moieties. In mice, when administered in subcutaneous, intramuscular or intraperitoneal regions, around 50% of SQL70 was detectable after 2 weeks at the injection site. Biodistribution results suggested clearance of SQL70 by hepatic and renal routes. The MTD of SQ3370 in mice was nearly 20-times that of conventional Dox. Anti-tumor efficacy was evident even at 0.37x the MTD of SQ3370 suggesting that increasing the SQ3370 dosage to its MTD can maximize therapeutic benefit. Safety evaluation in 72 dogs that received either SQL70 biopolymer alone, SQP33 protodrug alone or both together (SQ3370) showed that all agents were well tolerated. The Highest Non-Severely Toxic Dose (HNSTD) of SQ3370 was 8.95 mg/kg/cycle in Dox Eq, at which dose there were minimal systemic adverse events and no evidence of cardiotoxicity. (The standard veterinary clinical dose for Dox in dogs is 1 mg/kg/cycle). The PK profiles in dogs demonstrated that SQL70 biopolymer efficiently captures the protodrug from circulation and releases active Dox. In conclusion, the CAPAC Platform represents a new therapeutic modality to treat solid tumors by using a drug with known efficacy, such as doxorubicin, and expanding its pharmacological capabilities. The CAPAC Platform enables higher concentrations of the active drug at the tumor site and minimizes systemic adverse effects associated with conventional chemotherapy. SQ3370 is currently being evaluated in a Phase I study in patients with advanced solid tumors (https://clinicaltrials.gov/ct2/show/NCT04106492). Citation Format: Sangeetha Srinivasan, Nathan A. Yee, Amir Mahmoodi, Michael Zakharian, M. Wayne Saville, Jose M. Mejia Oneto. The CAPAC Platform maximizes therapeutic benefit and reduces systemic cytotoxic exposure in small and large animals [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1347.

First-in-human phase 1 dose escalation study of HX009, a novel recombinant humanized anti-PD-1 and CD47 bispecific antibody, in patients with advanced malignancies.

2517 Background: HX009 is a novel humanized antibody fusion protein which binds to CD47 and PD-1 concurrently. HX009 significantly inhibited tumor growth in mouse xenograft models. In Cynomolgus monkeys, the highest non-severely toxic dose in repeat dose testing was 15mg/kg. HX009-I-01 (ClinicalTrials.gov：NCT04097769) is a first-in-human study evaluating the safety and efficacy of HX009 in subjects with advanced malignancies. Here we report the preliminary results from this study. Methods: The study is being conducted in Australia at 3 sites. The study design follows a 3+3 dose-escalation scheme, enrolling cohorts of at least 3 subjects (except the first dose level) sequentially until MTD or the maximum dose is reached. HX009 is administered as single agent every 2 weeks via intravenous infusion. The 7 dose levels planned are: 0.1mg/kg (1 subject), 0.3mg/kg, 1mg/kg, 2mg/kg, 3mg/kg, 5mg/kg, 7.5mg/kg. All AEs are graded using NCI CTCAE v5.0. Efficacy assessments are per RECIST 1.1. Blood samples are obtained for pharmacokinetics (PK) and for immunogenicity assessments by the development of Antidrug Antibodies. Results: As of the January 22 2021 cutoff date, 21 patients (12M/9F) with a median age of 69.0 years (range 38-86) have received dose levels of 0.1-7.5 mg/kg. Patients with the following tumor types have been enrolled: colorectal cancer (7), squamous cell carcinoma (3), endometrial cancer (2), breast cancer (3), malignant epithelioid mesothelioma (1), gallbladder cancer (1), pancreatic cancer (1), glioblastoma(1), ovarian cancer (1), gastroesophageal junction adenocarcinoma (1). Patients had received a median of 3 (range 1-9) prior anti-cancer regimens. Treatment-related AEs have been reported in 10 (47.6%) patients to date. Most AEs are grade 1 or 2. The most frequent treatment-related AEs include nausea (n = 2, G1), rash (n = 2, G1), vomiting (n = 2, G1), and decreased appetite (n = 2, G1). Only 1 treatment-related SAE of pneumonitis. One treatment-related anemia (G2), and no thrombocytopenia. No DLT was observed in all 7 dose levels. Among 18 patients who have had at least one post-baseline tumor assessments, partial responses (PR) have been achieved in 3 patients with the following tumor types (dose level): gallbladder adenocarcinoma (1mg/kg), triple negative breast cancer (5mg/kg), metastatic squamous cell carcinoma of head and neck (5mg/kg). In addition, there are 6 patients with best overall response of stable disease. As of the data cutoff date, 6 patients are still receiving treatment. Updated clinical and PK results will be presented at the meeting. Conclusions: HX009, on an every 2 weeks dosing schedule, up to 7.5 mg/kg, is well-tolerated, without any DLT to date. Antitumor activity was seen at 1 mg/kg and 5 mg/kg cohorts with objective responses in multiple tumor types; Further investigation in phase Ib/II studies is warranted. Clinical trial information: NCT04097769.

Assessment of the toxicity and toxicokinetics of the novel potent tropomyosin receptor kinase (Trk) inhibitor LPM4870108 in rhesus monkeys

LPM4870108 is a tropomyosin receptor kinase (Trk) inhibitor that is currently under consideration for human clinical trials. We characterized the toxicity and toxicokinetic properties of LPM4870108 following its oral administration to rhesus monkeys (5, 10, or 20 mg/kg/day for 4 weeks with a 4-week recovery period). No evidence of LPM4870108 toxicity was observed over this study as reflected by an absence of difference in body weight, ophthalmoscopy, urinalysis, gross, or histopathology findings. No significant differences in toxicity-related outcomes were detected when comparing LPM4870108 and control groups, and no significant treatment-related changes in food consumption, electrocardiogram results, blood pressure, hematological parameters, biochemical values, organ weight, or bone marrow parameters were observed. Treatment caused dose-dependent effects of gait disturbance, impaired balance, poor coordination, and decreased grip strength in all LPM4870108-treated animals, with these effects being attributable to excessive on-target Trk receptor inhibition. After the 4-week recovery period, all these abnormal treatment-related findings had fully or partially resolved. The toxicokinetic study of monkeys revealed that the LPM4870108 exposure increased with dose. Overall, LPM4870108 exhibited a safety profile in treated monkeys, indicating that the Highest Non-Severely Toxic Dose (HNSTD) for LPM4870108 in monkeys was 20 mg/kg/day.

EXTH-71. IND-ENABLING CHARACTERIZATION OF ONC206 AS THE NEXT BITOPIC DRD2 ANTAGONIST FOR NEURO-ONCOLOGY

Abstract ONC201 is the first clinical bitopic antagonist of DRD2, an oncogenic receptor in brain and neuroendocrine tumors. ONC206, a derivative of ONC201 that shares the imipridone core structure, is also a bitopic DRD2 antagonist that exhibits enhanced non-competitive effects, high specificity, nanomolar potency, and disruption of DRD2 homodimers. Broad nanomolar efficacy of ONC206 (GI50 < 78-889nM, CellTitre-Glo, 72h) was observed in >1,000 GDSC cancer cell lines. Maximal ONC206 sensitivity was observed in pheochromocytoma, high-grade gliomas, neuroblastoma, medulloblastoma, sarcoma and cholangiocarcinoma cell lines exhibiting a DRD2+/DRD5- RNA expression signature. An exposure time of 48h at nanomolar concentrations was sufficient for maximal inhibition of tumor cell viability. ONC206 reduced the viability of normal human fibroblasts at higher doses (GI50 > 5µM), suggesting a wide therapeutic window. Antitumor efficacy without body weight loss was observed with 50 mg/kg weekly oral ONC206 in a dopamine-secreting HuCCT1 cholangiocarcinoma subcutaneous xenograft model. Biodistribution studies in Sprague-Dawley rats revealed a ~12 µM plasma Cmax with a systemic terminal half-life of ~6 hours upon a single oral dose of 50 mg/kg. Additionally, 5–10 fold higher ONC206 concentrations were observed in adrenal gland, bile duct, brain and bone marrow relative to plasma. Nanomolar concentrations were also observed in the CSF above DRD2 antagonism thresholds, unlike ONC201. GLP toxicology studies with weekly oral ONC206 in Sprague-Dawley rats and beagle dogs revealed no dose-limiting toxicities. Mild and reversible decreased body weight and/or body weight gain with no effects on food consumption were observed at the highest evaluated dose in both species. The highest non-severely toxic dose (HNSTD) was ≥ 16.7 mg/kg in dogs and ≥ 50 mg/kg in rats that exceeds efficacious doses in preclinical models. Using standard allometric scaling, a 90 mg starting dose of ONC206 was selected for the first-in-human clinical trial in biomarker-defined adult recurrent CNS tumors.

An FDA oncology analysis of toxicities associated with PBD-containing antibody-drug conjugates

With a new generation of antibody-drug conjugates (ADCs) that contain a drug-to-antibody ratio (DAR) of 2, the question remains whether advances in technology have resulted in more stable and tumor-specific ADCs. These ADCs are anticipated to cause minimal systemic exposures of payloads, with toxicities being evident mainly at tumor sites. We examined 15 ADCs with PBD-dimer payloads and a DAR of 2 and concluded that dose limiting toxicities in animals and in humans are generally related to the payload. Both the payloads and the ADCs had pro-inflammatory responses causing severe toxicities that were at times of low incidence, making it difficult to assess a cause-effect relationship. Due to their low incidence, single-patient cohorts may not detect these events and such design may not be suitable in first-in-human (FIH) trials. The commonly proposed approach by the sponsors for FIH dose selection was 1/6th highest non-severely toxic dose (HNSTD) in monkeys. This approach resulted in an acceptable balance of safety and efficient dose escalation in phase 1 trials, when using data from repeat-dose toxicology studies and body surface area for scaling. No sponsor used the data generated in rodents or proposed novel approaches for FIH dose selection.

Abstract 3901: Nonclinical safety evaluation of CA102N, a hyaluronic acid (HA) and nimesulide (Nim) conjugate, for colorectal cancer treatment

Abstract CA102N is a conjugate of the biological polymer hyaluronic acid (HA) and Nimesulide (Nim), a cyclooxygenase-2 (COX-2) inhibitor that represents a promising new approach to addressing cancer treatment. Similar to an antibody-drug conjugate or a pro-drug, CA102N enhances the efficacy of Nim through targeting and binding of HA to CD44 receptors highly expressed in solid tumors. Pharmacological (in vitro and in vivo) studies indicated that CA102N exhibits apoptotic and tumor growth inhibitory activities against colorectal cancer. The MOA of CA102N was demonstrated to be related to apoptosis and disruption of the PI3K/Akt/mTOR pathway in addition to inhibition of the COX-2/PGE2 related pathways. Safety of CA102N was assessed in acute dose range finding and repeat-dose intravenous toxicity studies in rats and beagle dogs. Three dose levels including the Maximum Tolerated Dose (MTD) from DRF study, a middle dose and a low dose equivalent to the proposed clinical dose were administered twice weekly (BID). A 28-day recovery group was also included in the rat study. Overall CA102N was well tolerated in both species. CA102N did not induce any significant effects on the CNS, the cardiovascular and respiratory systems in animal models. Some changes in hematological parameters were observed only in rats at the highest dose (Std 10: ≥ 600 mg/kg/day ), however, most of these observations were reversible. No hERG inhibition (in vitro) was observed suggesting the risk of QT prolongation with CA102N is low. The Highest Non-Severely Toxic Dose (HNSTD) of CA102N in the dog was determined to be 280 mg/kg/day (7.24 mg/kg in Nim equivalents ) and the rat NOAEL was 400 mg/kg/day (10.16 mg/kg in Nim equivalents ). These doses are 2.3 times (rat) and 5.6 times (dog) of nimesulide dose to be evaluated (up to 0.72 mg/kg of nimesulide) in the proposed phase 1 study. On the basis of the mechanism of action and the nonclinical safety profiles, toxicity associated risks to patients appear to be low at the proposed clinical dose levels. A Phase I study of CA102N in patients with locally advanced or metastatic colorectal cancer is ongoing. Citation Format: Eskouhie Tchaparian, Louis Lin, Elin Hsu, Ivy Chen, Albert Wu. Nonclinical safety evaluation of CA102N, a hyaluronic acid (HA) and nimesulide (Nim) conjugate, for colorectal cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3901.