Abstract 1533: IMGC936, a first-in-class ADAM9-targeting antibody-drug conjugate, demonstrates promising anti-tumor activity

Dysregulation of ADAM9, a member of the ADAM (a disintegrin and metalloproteinase) family of proteases, has been implicated in tumor progression and metastasis, as well as pathological neovascularization. ADAM9 overexpression correlates with poor prognosis in multiple cancers. We have shown that ADAM9 is overexpressed in multiple solid tumor indications and that anti-ADAM9 antibodies are efficiently internalized and degraded by tumor cell lines making ADAM9 an attractive target for antibody-drug conjugate (ADC) development. Here, we describe IMGC936, the first ADAM9-targeting ADC to enter preclinical development. IMGC936 is comprised of a high-affinity humanized antibody site-specifically conjugated to DM21, a next-generation linker-payload that combines a maytansinoid microtubule-disrupting payload with a stable peptide linker at a drug-antibody ratio of two. To maximize the potential for IMGC936 activity, the M252Y/S254T/T256E (YTE) mutation was introduced into the CH2 domain of the antibody to increase in vivo plasma half-life and exposure. In vitro studies demonstrated targeted cytotoxicity of IMGC936 across a panel of ADAM9-positve tumor cell lines with activity at least 2 logs greater than a non-targeting conjugate. Consistent with the in vitroactivity, an anti-ADAM9-DM21 conjugate displayed compelling anti-tumor activity in multiple xenograft models representing non-small cell lung, gastric and colorectal cancers. For example, in the EBC-1 non-small cell lung cancer subcutaneous xenograft model with only moderate ADAM9 expression (H-score of 130), anti-ADAM9-DM21 not only induced tumor growth delay but produced complete and durable remissions in 6/6 mice following a single intravenous dose of 8.6 mg Ab/kg (100 ug DM21/kg). IMGC936 demonstrated a favorable pharmacokinetic profile with good conjugate stability in non-human primates. Importantly, IMGC936 was well-tolerated following repeat dosing in cynomolgus monkeys with no ADAM9 target-related toxicities identified at doses exceeding the levels required for anti-tumor activity in murine xenograft models. Based on the totality of the preclinical data, IMGC936 represents a promising therapeutic candidate to target a wide range of ADAM9-expressing tumors.

Citation Format: Stuart Hicks, Deryk Loo, Kerstin Sinkevicius, Juniper Scribner, Bhaswati Barat, Nicholas Yoder, Christopher Espelin, Marian Themeles, Francine Chen, Jacquelynn Lucas, Jennifer Brown, Bahar Matin, Megan Fuller, Jenny Lee, Paulin Salomon, Juliet Costoplus, Sadiqa Yancey, Gundo Diedrich, Sergey Gorlatov, Thomas Son, Michael Chiechi, Pam Li, Michael Spliedt, Valentina Ciccarone, Jeff Hooley, Nadia Gantt, James Tamura, Kerry Donahue, Paul Moore, Syd Johnson, Thomas Chittenden, Richard Gregory, Ezio Bonvini. IMGC936, a first-in-class ADAM9-targeting antibody-drug conjugate, demonstrates promising anti-tumor activity [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 1533.

Abstract 38: Target validation, antibody discovery and preclinical data supporting ADAM9 as an antibody-drug conjugate therapeutic target for solid tumors

Introduction: A target-unbiased approach based on intact cell immunizations with fetal progenitor cells and cancer stem cells, followed by an immunohistochemistry (IHC) screen for cancer-specific candidates, led to the identification of anti-ADAM9 (a disintegrin and metalloproteinase) mAbs with highly differential tumor-versus-normal tissue binding. ADAM9 is a cell surface protein over-expressed in multiple tumors, with a possible role in promotion and progression of cancer through multiple mechanisms, including modulation of adhesion and migration as well as processing of tumorigenic and pro-angiogenic factors. In this preclinical study, we performed target/mAb validation and evaluated the therapeutic potential of anti-ADAM9 antibody-drug conjugates (ADCs) toward ADAM9-expressing solid cancers.

Methods: IHC was performed with anti-ADAM9 mAbs to confirm and extend available data of human normal and tumor tissue expression. Epitope mapping studies were conducted to define epitope-specificity. mAbs were also screened to identify those that efficiently internalized into tumor cells. In vitro cellular processing studies were performed to further evaluate the mAbs as ADC candidates. Selected mAbs were converted to ADCs via chemical conjugation to potent anti-microtubule (DM4) or DNA alkylating (DGN549) agents; in vitro cytotoxicity studies were conducted with tumor cell lines representing human cancer types that overexpress ADAM9. A lead mAb was then selected for humanization and affinity maturation to yield a development candidate.

Results: Anti-ADAM9 mAbs exhibited strong reactivity toward the tumor epithelium of solid cancers, including pancreatic, kidney, prostate, bladder, breast, colon, lung, and ovarian cancer, but limited reactivity toward normal tissues. Anti-ADAM9 mAbs were efficiently internalized and processed by tumor cell lines, including lines with only modest ADAM9 expression. Anti-ADAM9 ADCs exhibited specific, dose-dependent cytotoxicity toward ADAM9-positive cancer cell lines in vitro, with IC50 values in the sub-nanomolar range. Humanization and affinity maturation of the lead mAb yielded a development candidate that retains potent antitumor activity toward ADAM9-positive tumor cell lines and equivalent, high affinity binding to both human and cynomolgus monkey ADAM9.

Conclusion: ADAM9 is a cell surface antigen that is over-expressed on a wide range of solid cancers. Anti-ADAM9 mAbs that were strongly reactive with representative tumors exhibited high affinity for the antigen and were efficiently internalized and processed by ADAM9-bearing tumor cells. Anti-ADAM9 ADCs demonstrated dose-dependent cytotoxicity in vitro toward a panel of ADAM9-positive tumor cell lines. Our findings demonstrate that an ADC targeting ADAM9 may serve as a potential therapeutic for ADAM9-expressing solid tumors.

Citation Format: Juniper A. Scribner, Bhaswati Barat, Stuart W. Hicks, Nicholas C. Yoder, Thomas Son, Lusiana Widjaja, Gundo Diedrich, Sergey Gorlatov, Jeff Hooley, Ann Easton, Peter Lung, Anushka De Costa, Francine Chen, Michael Chiechi, Pam Li, Monica Licea, Timothy E. Hotaling, Michael Spliedt, Valentina Ciccarone, Nadia Gantt, James Tamura, Megan E. Fuller, Molly McShea, Scott Koenig, Syd Johnson, Paul A. Moore, Ezio Bonvini, Deryk Loo. Target validation, antibody discovery and preclinical data supporting ADAM9 as an antibody-drug conjugate therapeutic target for solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 38. doi:10.1158/1538-7445.AM2017-38

Abstract 1489: Development of a humanized ROR1 x CD3 bispecific DART® molecule for the treatment of solid and liquid tumors

Introduction: The receptor tyrosine kinase-like orphan receptor 1 (ROR1) is overexpressed in chronic lymphocytic leukemia and a subset of solid tumors, including lung, breast, ovarian, colon, and pancreatic cancers, as well as sarcoma. Limited adult tissue expression and its absence in normal leukocytes makes ROR1 a promising cancer therapeutic target. We have developed a Dual-Affinity Re-Targeting (DART®) protein for redirecting T lymphocytes to lyse tumor cells via monovalent recognition of ROR1 on tumors and CD3 on T cells. ROR1 x CD3 DART protein was engineered for improved half-life with the incorporation of a modified Fc domain, lacking effector function.

Methods: The ROR1 x CD3 DART protein was stably expressed in CHO cells and purified to homogeneity by a standard antibody platform. Bispecific binding was evaluated by ELISA and SPR analysis. In vitro functional studies were performed with lymphoma and solid tumor cell lines in the presence of primary human T cells. Tumor growth inhibition was evaluated in NOD/SCID/IL-2 gamma chain KO (NOG) mice coimplanted with human T cells and either mantle cell lymphoma (MCL) or lung cancer cell lines (5:1 effector : target cell ratio) followed by treatment with ROR1 x CD3 DART protein by intravenous (IV) administration. In vivo activity was also evaluated in human PBMC-reconstituted NOG/B2m deficient mice bearing established intradermal tumor xenografts following IV treatment with ROR1 x CD3 DART molecule. Pharmacokinetic analysis of the DART molecule was performed in human neonatal Fc receptor (hFcRn) transgenic mice.

Results: The ROR1 x CD3 DART protein displayed the expected bispecific binding for ROR1 and CD3 antigens and retained the affinity and specificity of the parent mAbs. The DART molecule mediated dose-dependent lysis of ROR1-positive MCL and solid tumor (breast, lung, and osteosarcoma) cell lines through recruitment of human T cells. DART molecule-mediated killing of ROR1-expressing target cells was accompanied by target-dependent T-cell activation and cytokine release; however, no activity was observed in the absence of target cells and no cytokine release was observed with human PBMCs alone. The ROR1 x CD3 DART protein displayed extended circulating half-life after administration to hFcRn-transgenic mice. In mouse efficacy studies, the growth of HBL-2 (MCL), HOP-92 (lung cancer), or NIH-1975 (a lung cancer line resistant to erlotinib) cells co-implanted with human T cells in NOG mice was inhibited by treatment with the ROR1 x CD3 DART protein at doses in the mcg/kg range. The ROR1 x CD3 DART molecule also demonstrated antitumor activity with high complete response rates in human PBMC-reconstituted mice bearing established HBL-2 cell xenografts.

Conclusion: The promising in vitro and in vivo activity of the Fc-bearing ROR1 x CD3 DART molecule supports further investigation as a potential candidate for the cancer treatment.

Citation Format: Bhaswati Barat, Gurunadh Chichili, Valentina Ciccarone, James Tamura, Sergey Gorlatov, Michael Spliedt, Francine Chen, Scott Koenig, Paul Moore, Ezio Bonvini, Ralph Alderson, Syd Johnson. Development of a humanized ROR1 x CD3 bispecific DART® molecule for the treatment of solid and liquid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1489.