Two poster presentations at the American Association for Cancer Research (AACR) 2023 Annual Meeting, being held April 14-19, 2023 at the Orange County Convention Center in Orlando, Florida, highlight late-breaking preclinical data from studies with an anti-Nectin-4 ADC and anti-HER2 ADC.

Both ADCs, being developed by Araris Biotech, a spin-off company from the Paul Scherrer Institute (PSI) and ETH Zurich, are generated using the company’s proprietary linker technology. This linker technology platform enables the conjugation of any drug payload to “off the shelf” antibodies, without the need for prior antibody engineering.

Results from two head-to-head in-vivo studies, presented during the 2023 annual AACR meeting, demonstrated that the two ADCs showed very high activity at low doses and an improved therapeutic index compared to US Food and Drug Administration’s (FDA-) approved ADCs.

“The preclinical data highlighted in these two presentations demonstrate that we can develop stable and highly efficacious ADCs with a low drug-load that have an excellent exposure, which we believe may enable us to address key dose-limiting toxicities,” said Philipp Spycher, Ph.D., co-founder and chief executive officer of Araris Biotech.

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“Our ADCs have the potential to address challenges seen amongst other currently approved ADC therapies, such as limited efficacy and tolerability, in addition to being able to display favorable biophysical properties. We are looking forward to studying our linker technology further and continuing to advance our Nectin-4 program,” Spycher added.

Overall, based on available data, the Araris bioconjugation technology allows for the generation of tailor-made ADC candidates with improved therapeutic indices.

Anti-Nectin-4 ADC
Using Araris’ proprietary one-step peptide linker and site-specific enzymatic conjugation technology, researchers at Araris generated a novel anti-Nectin-4 ADC. The novel drug, comprised of  enfortumab as the targeting antibody, conjugated to monomethyl auristatin E (MMAE) as the payload, demonstrated superior anti-tumor activity and tolerability compared to enfortumab-vedotin (EV) in head-to-head in vitro and in vivo studies.

The resulting ADC had a drug-to-antibody-ratio (DAR) of approximately 2 and above 98 percent monomeric content. By comparison, the FDA’s approved enfortumab-vedotin (Padcev®; Astellas Pharma/Seagen) has a higher payload, with a DAR of 4.

Despite the lower drug load, the novel ADC demonstrated potent cell cytotoxicity similar to enfortumab-vedotin.  In addition, the investigational agent also demonstrated excellent stability in mouse, cynomolgus, and human sera exemplified by the absence of payload deconjugation or linker cleavage, while, in contrast, enfortumab-vedotin showed significant payload deconjugation.

Also, despite its high stability, the novel anti-Nectin-4 ADC releases the free active MMAE metabolite at comparable rate to enfortumab vedotin in human Cathepsin B or human liver-lysosome (HLL) enzyme cleavage assays.

Results of pharmacokinetic studies in rodents demonstrated that the novel ADC is also extremely stable in circulation in, leading to an intact ADC exposure profile comparable to the unmodified enfortumab parent antibody. No free payload was detectable in circulation during the 3 week study by LCMS-MRM.

In efficacy studies, using a SUM-190PT established breast cancer model, a single injection at a dose of 10 ug/kg normalized by payload, resulted in complete tumor regression lasting for more than 100 days, representing a very durable response or tumor eradication. In contrast, enfortumab vedotin, administered at the same payload dose, only demonstrated a short and transient (only 20 day) tumor regression with no animal reaching a complete response, with no animal (0/6) reaching a complete response.

Toxicity
Despite higher in vivo exposure and extremely efficient anti-tumor response at low payload doses, there was no increased toxicity from the novel anti-Nectin-4 ADC. Overall tolerability improved compared to enfortumab vedotin showing less neutropenia, skin involvement* and signs of toxicity.

The highest non-severely toxic dose (HNSTD) in 4-week repeat dose rat toxicity studies for the the novel ADC (25 mg/kg) was 5-fold higher compared to the HNSTD (5mg/kg) reported for enfortumab vedotin.

The preclinical study data impressively show that the the novel ADC has superior efficacy and durable anti-tumor response even at 3-fold lower payload dose compared to enfortumab vedotin. The improved efficacy in mice and tolerability in rates resulted in a 8-fold better therapeutic index TI for the novel ADC and offers the opportunity to develop a highly efficacious ADC having potentially lower dose-limiting toxicities such as peripheral neuropathy, rashes or neutropenia.

The poster will be presented by Isabella Attinger-Toller, Ph.D. co-founder and chief technology officer of Araris Biotech on April 18, 2023 from 9:00 a.m. to 12:30 p.m. ET. The poster will be presented  at poster board number 14, abstract number LB221.

Ant-HER2 ADC
Using the same proprietary one-step peptide linker and site-specific enzymatic conjugation technology, researchers at Araris also generated an anti-HER2 ADC.

In head-to-head in vitro and in vivo studies, the novel, anti-HER2 ADC, using a Topoisomerase 1 (Topo1) inhibitor as payload, showed superior anti-tumor efficacy compared to trastuzumab deruxtecan (Enhertu®; Daiichi Sankyo and Astra Zeneca).

The resulting, highly homogeneous ADCs had a drug-to-antibody-ratio (DAR) of 2. By comparison, the US Food and Drug Administration approved trastuzumab deruxtecan has a DAR of 8.

In in vitro assays on target positive cell-lines, the novel anti-HER2 ADC demonstrated potent cell-cytotoxicity in the low nM-range, as well as a pharmacokinetic-profile similar to the naked antibody, similar to the approved trastuzumab deruxtecan. In addition, the novel ADC showed excellent stability in mouse, cynomolgus and human sera exemplified by the absence of payload deconjugation or linker cleavage while trastuzumab deruxtecan showed significant payload loss during the 14 day incubation period. Trastuzumab deruxtecan also showed faster clearance.

Noteworthy is that, despite the improved stability, the kinetics for payload release was highly efficient in human Cathepsin B or human liver-lysosome (HLL) enzyme cleavage assays.

The available data showed that the novel anti-HER2 ADC was extremely stable in circulation as shown in pharmacokinetic studies in rodents, demonstrating an exposure profile similar to the unmodified trastuzumab parent antibody.

Furthermore, in efficacy studies using an established NCI-N87 colon cancer model (therapeutic setting), a single injection of the novel anti-HER2 ADC at a dose of 52 ug/kg (adjusted payload dose) induced superior anti-tumor activity compared to trastuzumab deruxtecan, injected at the same payload dose.

The novel anti-HER2 ADC demonstrated complete tumor regression of all tumors (7/7)  obtained at 104 ug/kg payload dose, which lasted throughout the whole study duration (total 80 days).  The novel ADC was also very well tolerated.

Based on these data, the researchers conclude that Araris’ Topo1 linker-payloads resulted in highly potent ADCs with very favorable biophysical properties and extremely efficient payload release as well as an antibody-like exposure profile making them ideal linker-payloads for solid tumor targeting.

The researchers also concluded that the low-drug load is favorable in avoiding excessive toxicities in non-targeted tissues.

The poster will be presented by Philipp Spycher, Ph.D. co-founder and chief executive officer of Araris Biotech on April 18, 2023 from 9:00 a.m. to 12:30 p.m. ET. The poster will be presented  at poster board number 12, abstract number LB219.

Note: * The skin toxicity being the dose-limiting toxicity of enfortumab vedotin in humans and rats.

Highlights of prescribing information
Enfortumab vedotin (Padcev®; Astellas Pharma/Seagen) [Prescribing Information]
Trastuzumab deruxtecan (Enhertu®; Daiichi Sankyo and Astra Zeneca)[Prescribing Information]

Reference
[1] Attinger-Toller I, Probst P, Bertrand R, Renard E, Stark R, Santimaria R, Grabulovski D, Schlereth B, Spycher PR. Novel peptide linker-based nectin-4 targeting ADC shows improved tolerability with long-lasting anti-tumor efficacy at low doses. In: Proceedings of the 114th Annual Meeting of the American Association for Cancer Research; 2023 April 14-19; Orlando, FL. Philadelphia (PA): AACR; 2023. Abstract/Poster nr LB221 / 14
[2] Attinger-Toller I, Fay R, Bertrand R, Probst P, Stark R, Santimaria R, Grabulovski D, Schlereth B, Spycher PR. Inducing significant and efficient tumor growth inhibition vs trastuzumab deruxtecan with low drug-load topoisomerase 1 inhibitor ADC using novel peptide linkers for payload conjugation.  In: Proceedings of the 114th Annual Meeting of the American Association for Cancer Research; 2023 April 14-19; Orlando, FL. Philadelphia (PA): AACR; 2023. Abstract/Poster nr LB219 / 12.

Featured image: Poster session during the Annual Meeting of the American Association for Cancer Research Annual Meeting, Sunday March 31, 2019. Photo courtesy © AACR/Todd Buchanan 2019

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