{"id":16928,"date":"2026-09-14T13:40:15","date_gmt":"2026-09-14T13:40:15","guid":{"rendered":"https:\/\/www.sygnaturediscovery.com\/blog\/toxicity-efficacy-in-adcs\/"},"modified":"2026-10-09T09:33:50","modified_gmt":"2026-10-09T09:33:50","slug":"toxicity-efficacy-in-adcs","status":"publish","type":"blog","link":"https:\/\/www.sygnaturediscovery.com\/fr\/blog\/toxicity-efficacy-in-adcs\/","title":{"rendered":"Toxicity & Efficacy in ADCs: How to Get it Right"},"content":{"rendered":"\n

Catch up on our ADC development series<\/a> on YouTube to hear more expert insights.<\/p>\n\n\n\n

ADC toxicity arises when the cytotoxic payload acts on healthy tissue alongside the tumor, often through premature release of the payload in the systemic circulation.<\/p>\n\n\n\n

Antibody-Drug Conjugates (ADCs) still face significant challenges related to patient tolerability and therapeutic window, and ADCs often fail to significantly reduce toxicity compared to traditional cytotoxic agents, highlighting the ongoing struggle to improve specificity and safety.<\/p>\n\n\n\n

Selective Targeting and Payload Design (\u2018Selectivity Squared\u2019) <\/strong><\/h2>\n\n\n\n

Traditional ADC payloads typically fall into three main classes, each designed to disrupt cancer cell survival through distinct mechanisms. Microtubule inhibitors, such as MMAE and DM1, interfere with spindle formation in mitosis. Auristatins such as MMAE bind to the side of forming spindles causing kinks which results in improper alignment, while maytansinoids bind to the spindle terminus directly inhibiting its growth. Topoisomerase I inhibitors, including DXd and SN-38, inhibit the topo 1 enzyme which helps to regulate DNA under- and over-winding to remove knots and tangles from the genetic material. Topo1 functions by creating tightly controlled single-stranded breaks in DNA, which are key to cell regulation and DNA replication. Meanwhile, DNA-damaging\/chelating agents\u2014often highly potent\u2014directly compromise DNA by binding into the minor groove and covalently bonding. <\/p>\n\n\n\n

A common trait with all the mechanisms employed by conventional ADC cytotoxic payload is that each is present in both healthy and disease state cells, thus limiting selectivity and substantially increasing systemic, payload-mediated ADC toxicity if the ADC is broken down outside the target cell.<\/p>\n\n\n\n

Increasing the therapeutic window may involve enhancing both the selectivity of the antibody and the specificity of the payload. Modifying linker chemistry<\/a> and optimizing payload conjugation are crucial, as even minor changes can drastically affect the balance between efficacy and toxicity. This is where the concept of a biologic\/chemical bispecific molecule comes into play. The combination of a highly specific antibody with a targeted small molecule therapeutic can maximize targeted action, an approach we informally refer to as \u201cselectivity squared\u201d. Rather than relying solely on the antibody for specificity, we\u2019re now integrating selectivity at multiple levels\u2014the antibody, the small molecule<\/a> payload, and even the linker. <\/p>\n\n\n\n

Multidisciplinary Approach to ADC Development <\/strong><\/h2>\n\n\n\n

Achieving this selectivity requires a multidisciplinary approach<\/a>, bringing together chemistry<\/a>, bioscience<\/a>, DMPK<\/a>, and both in vivo<\/em> efficacy<\/a> and ex vivo<\/em> PK to understand how subtle changes can have a significant impact on the overall therapeutic profile. We\u2019re used to developing small molecules and we\u2019re used to small changes having significant effects on PK and toxicity and overall therapeutic profile. <\/p>\n\n\n\n

It\u2019s no different in this emerging ADC paradigm. Every single atom change, linker adjustment, or payload modification can dramatically shift an ADC from a highly selective therapeutic to an ineffective or less selective compound. By embracing a holistic perspective<\/a>\u2014one that sees ADCs as hybrid molecules rather than just targeted delivery vehicles\u2014we can unlock new potential and rethink how selectivity is built from the ground up. <\/p>\n\n\n\n

Learn more about Sygnature’s ADC capabilities here<\/a>.<\/p>\n\n\n\n

Catch up on the full ADC development blog series:<\/strong><\/h3>\n\n\n\n

Part 1: Exploring new paths in ADC development<\/a><\/p>\n\n\n\n

Part 2: What’s the Evolving Role of Medicinal Chemistry in ADC Development?<\/a><\/p>\n\n\n\n

Part 3: Linker Technologies in ADCs: How They Impact Efficacy &<\/a> <\/a>Stability<\/a><\/p>\n\n\n\n

Part 5: 3 Transformative Changes in ADC Development Over the Next Decade<\/a><\/p>\n\n\n

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FAQs<\/h2>\n<\/div>\n<\/div>\n\n\n\n
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