Novel Anti-B-cell Maturation Antigen Alpha-Amanitin Antibody-drug Conjugate HDP-101 Shows Superior Activity to Belantamab Mafodotin and Enhanced Efficacy in Deletion 17p Myeloma Models

B-cell maturation antigen (BCMA) plays a pathobiologic role in myeloma and is a validated target with five BCMA-specific therapeutics having been approved for relapsed/refractory disease. However, these drugs are not curative, and responses are inferior in patients with molecularly-defined high-risk disease, including those with deletion 17p (del17p) involving the tumor suppressor TP53, supporting the need for further drug development. Del17p has been associated with reduced copy number and gene expression of RNA polymerase II subunit alpha (POLR2A) in other tumor types. We therefore studied the possibility that HDP-101, an anti-BCMA antibody drug conjugate (ADC) with the POLR2A poison α-amanitin could be an attractive agent in myeloma, especially with del17p. HDP-101 reduced viability in myeloma cell lines representing different molecular disease subtypes, and overcame adhesion-mediated and both conventional and novel drug resistance. After confirming that del17p is associated with reduced POLR2A levels in publicly available myeloma patient databases, we engineered TP53 wild-type cells with a TP53 knockout (KO), POLR2A knockdown (KD), or both, the latter to mimic del17p. HDP-101 showed potent anti-myeloma activity against all tested cell lines, and exerted enhanced efficacy against POLR2A KD and dual TP53 KO/POLR2A KD cells. Mechanistic studies showed HDP-101 up-regulated the unfolded protein response, activated apoptosis, and induced immunogenic cell death. Notably, HDP-101 impacted CD138-positive but not-negative primary cells, showed potent efficacy against aldehyde dehydrogenase-positive clonogenic cells, and eradicated myeloma in an in vivo cell line-derived xenograft (CDX). Interestingly, in the CDX model, prior treatment with HDP-101 precluded subsequent engraftment on tumor cell line rechallenge in a manner that appeared to be dependent in part on natural killer cells and macrophages. Finally, HDP-101 was superior to the BCMA-targeted ADC belantamab mafodotin against cell lines and primary myeloma cells in vitro, and in an in vivo CDX. Together, the data support the rationale for translation of HDP-101 to the clinic, where it is now undergoing Phase I trials, and suggest that it could emerge as a more potent ADC for myeloma with especially interesting activity against the high-risk del17p myeloma subtype.

Abstract 1761: Treatment with antibody-targeted amanitin conjugates induces tolerability in preclinical models without triggering tolerance

Background: Amatoxin-based antibody-drug conjugates (ATACs) are a new class of ADCs using amanitin, a specific inhibitor of RNA polymerase II, as toxic payload. A first ATAC targeting B-cell maturation antigen (BCMA) is currently being tested in phase I/II clinical trials in multiple myeloma patients. During the clinical trials, the effect of repeated dosing on safety as well as anti-tumor efficacy of the ATAC will be assessed. In preclinical studies a reduction of toxicity was observed after repeated dosing with ATACs regardless of the target or antibody. In the present study, we demonstrate the effect of ATAC pre-treatment on tolerability in pre-clinical models.

Material and Methods: Antibody: Engineered monoclonal antibodies produced at Heidelberg Pharma

Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibody.

Animal models: Tolerability in CB17 Scid mice and Cynomolgus monkeys; Efficacy in a subcutaneous LNCaP prostate cancer model; Treatment: ADC (ATAC): escalating dosing i.v. q21d (tolerability) or repeated dosing i.v. q7dx4 (efficacy).

Results: The impact of repeated dosing on the tolerability of a non-targeting ATAC was tested in CB17 Scid mice. The mice were initially treated with the maximal tolerated dose (MTD) of an ATAC, or PBS followed by a second higher dose 21 days after the first dose. Pre-treatment improved the tolerability of a second, higher dose of the same non-targeting ATAC from 12.5% to 80% survival.

As ATAC toxicity is mainly caused by liver toxicity, the liver damage markers AST, ALT and LDH are used as toxicity markers in non-human primate studies. The induction of liver damage markers observed after repeated or escalated dosing was significantly lower than the induction after single or first dose treatment. Taken together, these data indicate that ATAC treatment can induce tolerability in animal models. Furthermore, in a subcutaneous LNCaP prostate cancer model, multiple ATAC dosing did improve the anti-tumor efficacy as compared to single dose treatment, indicating that the induced tolerability is not associated with reduced anti-tumor efficacy.

Conclusions: ATAC pre-treatment induces tolerability in preclinical animal models without a loss in efficacy. Since this effect of ATAC pre-treatment was observed across different animal species, it likely translates also into humans. Consequently, if reduced liver toxicity and less adverse effects after repeated dosing with ATACs are also observed in the upcoming clinical trials, it might have a significant impact on treatment regimen and clinical success of ATACs.

Citation Format: Kristin Decker, Marisa Schmitt, Can Araman, Franziska Ebeling, Irina Dranova, Torsten Hechler, Anikó Pálfí, Andreas Pahl, Michael Kulke. Treatment with antibody-targeted amanitin conjugates induces tolerability in preclinical models without triggering tolerance [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 1761.

Abstract 1754: Amatoxin-based antibody-drug conjugates induce immunogenic cell death and improve the anti-tumor efficacy of immune checkpoint inhibitors in humanized mouse models

Background: Amatoxin-based antibody-drug conjugates (ATACs) comprise a new class of antibody-drug conjugates (ADCs) using amanitin as a toxic payload. Amanitin binds to the RNA polymerase II and thereby efficiently inhibits the cellular transcription process. In the present study, we show that ATACs belong to the class of immune activating drugs which exhibit synergistic anti-tumor efficacy with immune checkpoint inhibitors (ICIs) in vivo by induction of immunogenic cell death (ICD). ICIs are a new class of cancer therapeutics utilizing patients` immune system to kill cancer cells. ICIs rely on the activity of the immune system to develop their full potential. Therefore, drugs that are heating up cold tumors and make them visible to the patients` immune system and by that enhancing the anti-tumor efficacy of ICIs, e.g., ATACs, are on high demand for the treatment of tumor patients.

Material and methods: Cell line: Her2+ cell lines: NCI-N87; CD19+ cell line: Raji

Antibody: anti-Her2 and anti-CD19 engineered monoclonal antibody produced at Heidelberg Pharma

Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibody.

Animal models: Raji cells with human peripheral blood mononuclear cells (PBMCs), NCI-N87 cells or HCBx-10/HCBx-11 PDX (Xentech, France) tumor pieces were implanted subcutaneously in mice. Treatment: ATAC: single dose i.v.; immune checkpoint inhibitors: Q3Dx6 or Q3Dx5.

Results: In vivo treatment of heterogenous Her2low PDX tumors with an anti-Her2-ATAC led to a significant tumor growth delay and complete tumor remission. Furthermore, increased expression of HMGB1 and surface exposure of calreticulin (CRT), two hallmarks of ICD, was observed in the same PDX tumors as well as in a Her2+ CDX (NCI-N87) tumor after the treatment with an anti-HER2 ATAC. In addition, the combined treatment of ATACs and different ICIs targeting CTLA-4 (Ipilimumab), PD-L1 (Pembrolizumab) or PD-1 (Avelumab) had a synergistic effect in a humanized lymphoma CDX model in the presence of human PBMCs. Combination treatment led to enhanced tumor growth inhibition and more tumor free animals as compared to single treatments with ATAC or ICI.

Conclusions: The strong anti-tumor efficacy of ATACs even in heterogenous patient-derived xenograft models in combination with the induction of ICD in vitro and in vivo suggest that the anti-tumor effect of ATACs is accompanied by the activation of the immune system. This hypothesis is strengthened by the finding that ATACs and ICIs show a synergistic effect in vivo. The presented data highlights the general concept of the synergistic effect of ATACs and ICIs which applies to several types of ICIs thus strengthening the scientific rationale for combination treatments in clinical trials.

Citation Format: Christian Orlik, Franziska Ebeling, Kristin Decker, Irina Dranova, Anikó Pálfi, Christoph Mueller, Torsten Hechler, Andreas Pahl, Michael Kulke. Amatoxin-based antibody-drug conjugates induce immunogenic cell death and improve the anti-tumor efficacy of immune checkpoint inhibitors in humanized mouse models [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 1754.

AGR2-Dependent Nuclear Import of RNA Polymerase II Constitutes a Specific Target of Pancreatic Ductal Adenocarcinoma in the Context of Wild-Type p53

BACKGROUND & AIMS

Promoted by pancreatitis, oncogenic KrasG12D triggers acinar cells' neoplastic transformation through acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia. Anterior gradient 2 (Agr2), a known inhibitor of p53, is detected at early stage of pancreatic ductal adenocarcinoma (PDAC) development. RNA polymerase II (RNAPII) is a key nuclear enzyme; regulation of its nuclear localization in mammalian cells represents a potential therapeutic target.

METHODS

A mouse model of inflammation-accelerated KrasG12D-driven ADM and pancreatic intraepithelial neoplasia development was used. Pancreas-specific Agr2 ablation was performed to access its role in pancreatic carcinogenesis. Hydrophobic hexapeptides loaded in liposomes were developed to disrupt Agr2-RNAPII complex.

RESULTS

We found that Agr2 is up-regulated in ADM-to-pancreatic intraepithelial neoplasia transition in inflammation and KrasG12D-driven early pancreatic carcinogenesis. Genetic ablation of Agr2 specifically blocks this metaplastic-to-neoplastic process. Mechanistically, Agr2 directs the nuclear import of RNAPII via its C-terminal nuclear localization signal, undermining the ATR-dependent p53 activation in ADM lesions. Because Agr2 binds to the largest subunit of RNAPII in a peptide motif-dependent manner, we developed a hexapeptide to interfere with the nuclear import of RNAPII by competitively disrupting the Agr2-RNAPII complex. This novel hexapeptide leads to dysfunction of RNAPII with concomitant activation of DNA damage response in early neoplastic lesions; hence, it dramatically compromises PDAC initiation in vivo. Moreover, the hexapeptide sensitizes PDAC cells and patient-derived organoids harboring wild-type p53 to RNAPII inhibitors and first-line chemotherapeutic agents in vivo. Of note, this therapeutic effect is efficient across various cancer types.

CONCLUSIONS

Agr2 is identified as a novel adaptor protein for nuclear import of RNAPII in mammalian cells. Also, we provide genetic evidence defining Agr2-dependent nuclear import of RNAPII as a pharmaceutically accessible target for prevention and treatment in PDAC in the context of wild-type p53.

Iodine-Mediated Tryptathionine Formation Facilitates the Synthesis of Amanitins

Synthetic methods on the macrocyclization of peptides are of high interest since they facilitate the synthesis of various types of potentially bioactive compounds, e.g. addressing targets like protein-protein-interactions. Herein, we report on an efficient method to construct tryptathionine-cross-links in peptides between the amino acids Trp and Cys. This reaction not only is the basis for the total synthesis of the death cap toxin α-amanitin but also provides rapid access to various new amanitin analogues. This study for the first time presents a systematic compilation of structure-activity relations (SAR) of amatoxins with regard to RNA polymerase II inhibition and cytotoxicity with one amanitin derivative of superior RNAP II inhibition. The present approach paves the way for the synthesis of structurally diverse amatoxins as future payloads for antibody-toxin conjugates in cancer therapy.

Design, Synthesis, and Biochemical Evaluation of Alpha-Amanitin Derivatives Containing Analogs of the trans-Hydroxyproline Residue for Potential Use in Antibody-Drug Conjugates

Alpha-amanitin, an extremely toxic bicyclic octapeptide extracted from the death-cap mushroom, Amanita phalloides, is a highly selective allosteric inhibitor of RNA polymerase II. Following on growing interest in using this toxin as a payload in antibody-drug conjugates, herein we report the synthesis and biochemical evaluation of several new derivatives of this toxin to probe the role of the trans-hydroxyproline (Hyp), which is known to be critical for toxicity. This structure activity relationship (SAR) study represents the first of its kind to use various Hyp-analogs to alter the conformational and H-bonding properties of Hyp in amanitin.

Abstract 915: Preclinical evaluation of anti-CD37 antibody-targeted amanitin conjugates (ATAC) in B-cell malignancies

Background:

ATACs (antibody-targeted amanitin conjugates) comprise a new class of antibody-drug conjugates (ADCs) using amanitin as a toxic payload. Amanitin binds to the RNA pol II and thereby efficiently inhibits the cellular transcription process. In the current study, in vitro and in vivo data of ATACs targeting CD37 (member of the tetraspanin family) are presented. CD37 is a transmembrane protein expressed exclusively on cells of the immune system and mainly on mature B-cells, as well as in many B-cell malignancies, including Richter's Syndrome (RS) or Richter´s transformation. RS is a transformation of B cell chronic lymphocytic leukemia, refractory to treatment and carries a poor prognosis, and hence is considered an ideal target for amanitin-based ADCs.

Material and methods:

Cell lines: CD37-positive: Mec-2 (B-chronic lymphocytic leukaemia); Raji-Luc, Ramos (Burkitt´s lymphoma); CD37-negative: HL-60 (acute lymphocytic leukemia)

Antibody: anti-CD37 engineered monoclonal antibody produced at Heidelberg Pharma

Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibody.

Cell proliferation assay: Quantitative determination of cell viability was performed by CellTiter Glo 2.0 assay (Promega).

Animal models: Disseminating Mouse xenograft tumor models (Mec-2 and Raji-Luc) and CD37-positive patient derived xenograft (PDX; Richter's Syndrome) models were performed in single-dose experiments. Tolerability was assessed in non-human primates (NHP).

Results:

All tested anti-CD37 ATACs showed in vitro cytotoxicity in the picomolar range on CD37-positive cell lines. No cytotoxic activity was observed on CD37-negative cells.

In mouse xenograft models, 80 - 100% overall survival was achieved with two anti-CD37 ATACs at doses of 1/16 MTD (Mec-2 model) and 1/64 MTD (Raji Luc Model). Single-dose treatment caused rapid and complete tumor remission already 7 days after treatment.

The tested ATACs revealed good tolerability in mice.

In NHP, the anti CD37 ATACs revealed good tolerability. Hematology and clinical chemistry parameters were unaffected except liver transaminases and LDH: A mild to moderate and transient increase was observed.

Conclusions:

Targeted cytotoxic drug delivery to CD37 positive cell lines was achieved by using anti-CD37 ATACs. The mode of action of the payload amanitin led to an efficient anti-tumor potential in vitro and in vivo with good tolerability in non-human primates. Using ADCs in the therapy of B-cell lymphomas, including malignancies that underwent Richter's transformation, is a promising approach, especially by using a payload whose mode of action differs from other commonly used toxins, like ATACs.

Citation Format: Stephanie Voss, Aniko Palfi, Christoph Mueller, Andreas Pahl, Torsten Hechler, Michael Kulke. Preclinical evaluation of anti-CD37 antibody-targeted amanitin conjugates (ATAC) in B-cell malignancies [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 915.

Abstract 910: Amanitin-based ADCs targeting PSMA as novel therapeutic modality for prostate cancer therapy

Background:

Antibody-targeted amanitin conjugates (ATACs) comprise a new class of antibody-drug conjugates (ADCs) using amanitin as toxic payload. Amanitin binds to the RNA pol II and thereby efficiently inhibits the cellular transcription process. In the current study, in vitro and in vivo data of an ATAC targeting PSMA (prostate specific membrane antigen) are presented. PSMA is a type II integral membrane glycoprotein and used as tumor marker due to its predominant expression on malignant prostate cells in prostate carcinoma. As PSMA expression increases with tumor aggressiveness, metastatic and disease recurrence, it is considered an ideal target for amanitin-based ADCs.

Material and methods:

Cell lines: PSMA+ cell lines: LNCap, 22RV1; PSMA- cell line: PC3

Antibody: cysteine engineered monoclonal anti-PSMA antibody (Albert Ludwig University Freiburg, medical center; derivatization and production at Heidelberg Pharma)

Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to engineered cysteine residues of the anti-PSMA antibody yielding ATACs with a DAR of 2.

Cell proliferation assay: Quantitative determination of cell viability was performed by BrdU-based chemiluminescent cell proliferation ELISA (Roche).

Animal models: Subcutaneous Mouse xenograft tumor models with PSMA-positive cell lines 22RV1 and LNCap were performed in single-dose experiments. Tolerability was assessed in mice and non-human primates (NHP).

Results:

All anti-PSMA ATACs with optimized amanitin-linker variants for use in solid tumors showed favorable in vitro cytotoxicity with nano- to picomolar activity on PSMA+ cell lines and no cytotoxic activity on PSMA- cells.

In mouse xenograft models, the optimized anti-PSMA ATACs caused dose-dependent tumor regression in LNCap s.c. xenografts. Complete remission was achieved after a single i.v. dose of ¼ MTD with 100% overall survival for the full duration of the studies (>160 days).

The tolerability of the tested ATACs in mice differed between 15 and > 80 mg/kg

Safety profiling in Cynomolgus monkeys revealed a good tolerability and therapeutic index for all selected amanitin-linker variants. Hematology and clinical chemistry parameters were unaffected except liver enzymes and LDH: A moderate and transient increase was observed. Low off target toxicity was confirmed by a non-binding ATAC.

Conclusions:

Targeted cytotoxic drug delivery to PSMA positive cell lines was achieved by using anti-PSMA ATACs optimized for the use in solid tumors. The mode of action of the payload amanitin led to an efficient anti-tumor potential in vitro and in vivo with good tolerability in non-human primates. Using ATACs in the therapy of PSMA positive prostate cancer is a promising approach, especially by using a cytotoxic agent whose mode of action differs from other commonly used toxins.

Citation Format: Alexandra Braun, Aniko Palfi, Christoph Mueller, Torsten Hechler, Andreas Pahl, Michael Kulke. Amanitin-based ADCs targeting PSMA as novel therapeutic modality for prostate cancer therapy [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 910.

Abstract 921: Combination of antibody-targeted amanitin conjugates (ATAC) with immune checkpoint inhibitors shows synergistic therapeutic effect in vitro and in vivo

Background:

Antibody-targeted amanitin conjugates (ATACs) are a new class of antibody-drug conjugates (ADCs) using amanitin as a toxic payload. Amanitin binds to the RNA polymerase II and thereby efficiently inhibits the cellular transcription process. The present study highlights the benefit of combining ATACs with immune checkpoint inhibitors. The combination of these two modalities leads to an induction of immunogenic cell death (ICD) in vitro and a synergistic anti-tumor effect in vivo. Hence, the combination of ATACs with immune checkpoint inhibitors (ICI) provides a promising approach for potential further cancer treatment.

Material and methods:

Cell lines: BT-474 (breast ductal carcinoma); BJAB, Raji, (Burkitt lymphoma)

Antibody: engineered monoclonal antibody produced at Heidelberg Pharma

Toxic warhead: Cysteine reactive amanitin-linker constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibody.

Animal models: Raji cells with/without human peripheral blood mononuclear cells (PBMCs) were implanted subcutaneously in mice. Treatment: ADC (ATAC): single dose i.v.; immune checkpoint inhibitor: Q3D x6.

Results:

The treatment of target-positive cell lines (e.g., BT-474 and BJAB) with corresponding ATACs led to the induction of three ICD hallmarks in vitro. In addition to increased surface expression of calreticulin (CRT), ATAC-treated tumor cells secreted adenosine triphosphate (ATP) and released high-mobility group box 1 protein (HMGB1). In contrast, this was not observed when the same cells were treated with a non-targeting ATAC.

In a subcutaneous CDX model, mixed with human PBMCs, the combined administration of target specific ATACs with an immune checkpoint inhibitor led to an increased anti-tumor effect indicated by significant tumor growth inhibition as compared to single treatment with ATAC or ICI. This synergistic effect was not observed in mice bearing tumors without human PBMCs.

Conclusions:

Antibody-targeted amanitin conjugates (ATACs) induced immunogenic cell death in vitro and resulted in an increased anti-tumor effect in combination with an immune checkpoint inhibitor in a subcutaneous CDX model if human PBMCs were present.

Consequently, the data presented provide a rationale to the use of ATACs in combination therapy with immune checkpoint inhibitors.

Citation Format: Kristin Decker, Irina Dranova, Christian Orlik, Aniko Palfi, Christoph Mueller, Ram Kumar Singh, Robert Z. Orlowski, Torsten Hechler, Andreas Pahl, Michael Kulke. Combination of antibody-targeted amanitin conjugates (ATAC) with immune checkpoint inhibitors shows synergistic therapeutic effect in vitro and in vivo [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 921.

Enhancing the Pharmacokinetics and Antitumor Activity of an α-Amanitin-Based Small-Molecule Drug Conjugate via Conjugation with an Fc Domain

Herein we describe the design and biological evaluation of a novel antitumor therapeutic platform that combines the most favorable properties of small-molecule drug conjugates (SMDCs) and antibody drug conjugates (ADCs). Although the small size of SMDCs, compared to ADCs, is an appealing feature for their application in the treatment of solid tumors, SMDCs usually suffer from poor pharmacokinetics, which severely limits their therapeutic efficacy. To overcome this limitation, in this proof-of-concept study we grafted an α-amanitin-based SMDC that targets prostate cancer cells onto an immunoglobulin Fc domain via a two-step "program and arm" chemoenzymatic strategy. We demonstrated the superior pharmacokinetic properties and therapeutic efficacy of the resulting Fc-SMDC over the SMDC in a prostate cancer xenograft mouse model. This approach may provide a general strategy toward effective antitumor therapeutics combining small size with pharmacokinetic properties close to those of an ADC.

Targeted immunotherapy for HER2-low breast cancer with 17p loss

The clinical challenge for treating HER2 (human epidermal growth factor receptor 2)-low breast cancer is the paucity of actionable drug targets. HER2-targeted therapy often has poor clinical efficacy for this disease due to the low level of HER2 protein on the cancer cell surface. We analyzed breast cancer genomics in the search for potential drug targets. Heterozygous loss of chromosome 17p is one of the most frequent genomic events in breast cancer, and 17p loss involves a massive deletion of genes including the tumor suppressor TP53 Our analyses revealed that 17p loss leads to global gene expression changes and reduced tumor infiltration and cytotoxicity of T cells, resulting in immune evasion during breast tumor progression. The 17p deletion region also includes POLR2A, a gene encoding the catalytic subunit of RNA polymerase II that is essential for cell survival. Therefore, breast cancer cells with heterozygous loss of 17p are extremely sensitive to the inhibition of POLR2A via a specific small-molecule inhibitor, α-amanitin. Here, we demonstrate that α-amanitin-conjugated trastuzumab (T-Ama) potentiated the HER2-targeted therapy and exhibited superior efficacy in treating HER2-low breast cancer with 17p loss. Moreover, treatment with T-Ama induced immunogenic cell death in breast cancer cells and, thereby, delivered greater efficacy in combination with immune checkpoint blockade therapy in preclinical HER2-low breast cancer models. Collectively, 17p loss not only drives breast tumorigenesis but also confers therapeutic vulnerabilities that may be used to develop targeted precision immunotherapy.

HDP-101, an Anti-BCMA Antibody-Drug Conjugate, Safely Delivers Amanitin to Induce Cell Death in Proliferating and Resting Multiple Myeloma Cells

Despite major treatment advances in recent years, patients with multiple myeloma inevitably relapse. The RNA polymerase II complex has been identified as a promising therapeutic target in both proliferating and dormant cancer cells. Alpha-amanitin, a toxin so far without clinical application due to high liver toxicity, specifically inhibits this complex. Here, we describe the development of HDP-101, an anti-B-cell maturation antigen (BCMA) antibody conjugated with an amanitin derivative. HDP-101 displayed high efficacy against both proliferating and resting myeloma cells in vitro, sparing BCMA-negative cells. In subcutaneous and disseminated murine xenograft models, HDP-101 induced tumor regression at low doses, including durable complete remissions after a single intravenous dose. In cynomolgus monkeys, HDP-101 was well tolerated with a promising therapeutic index. In conclusion, HDP-101 safely and selectively delivers amanitin to myeloma cells and provides a novel therapeutic approach to overcome drug resistance in this disease.

β-Glucuronidase triggers extracellular MMAE release from an integrin-targeted conjugate

A non-internalizing αvβ3 integrin ligand was conjugated to the anticancer drug MMAE through a β-glucuronidase-responsive linker. In the presence of β-glucuronidase, only the conjugate bearing a PEG4 spacer inhibited the proliferation of integrin-expressing cancer cells at low nanomolar concentrations, indicating important structural requirements for the efficacy of these therapeutics.

Amatoxins as RNA Polymerase II Inhibiting Antibody–Drug Conjugate (ADC) Payloads

Amatoxins are a group of natural toxins which occur in the death cap mushroom (Amanita phalloides). They work by inhibiting RNA polymerase II, which results in apoptosis. RNA-polymerase II inhibition is a novel mechanism of action in cancer therapy and offers the possibility of breaking through drug resistance or destroying dormant tumour cells, which could produce major clinical advances. Amanitin, as the most potent member of this toxin family, has been made accessible for cancer therapy by developing it as a payload for antibody–drug conjugates (ADCs). This chapter describes the discovery and chemistry of the amatoxins, and the development of the amanitin-ADC technology.

Abstract 237: Preclinical evaluation of anti-HER2 Antibody Targeted Amanitin Conjugates (ATACs) on HER2low breast cancer with chromosome 17p deletion

Background:

Triple negative breast cancer (TNBC) is the most difficult to treat subtype of breast cancer with limited therapeutic options. At least 50% of TNBC patients have low epidermal growth factor receptor 2 (HER2; ERBB2) expression with the majority harboring hemizygous loss of POLR2A/chromosome 17p. For these patients the treatment with antibody-targeted amanitin conjugates (ATACs) targeting HER2 is a new promising approach. ATACs comprise a new class of antibody-drug conjugates (ADCs) using amanitin as toxic payload and are able to kill antigen low expressing cells. Amanitin binds to the eukaryotic RNA polymerase II and thereby efficiently inhibits the cellular transcription process. In the current study, in vitro and in vivo data of ATACs targeting human HER2low as well as tolerability studies are presented. HER2low TNBC is considered an interesting target for amanitin-based ADCs.

Material and methods:

Different HER2 expressing cell lines were treated with anti-HER2 ATACs. Cysteine reactive amanitin-linkers were conjugated site-specifically to engineered cysteine residues of an anti-HER2 antibody yielding ATACs with a DAR of 2.0. Quantitative determination of cell viability was analyzed by BrdU ELISA assay. Subcutaneous mouse xenograft models with HER2-positive cell lines were performed with single-dose treatments. In addition, ATAC efficacy was tested in HER2low heterogeneous TNBC patient derived xenograft (PDX) models with and without POLR2A deletion. Tolerability of ATACs was assessed in mice and non-human primates (NHP).

Results:

Anti-HER2 ATACs showed in vitro cytotoxicity on HER2+ high and low cell lines in low nanomolar to picomolar range. In mouse xenograft models, the anti-HER2 ATACs caused dose-dependent tumor regression independent of Her2 expression level. In HER2low heterogeneous TNBC PDX models anti-HER2 ATACs caused dose-dependent tumor regression. The efficacy of anti-Her2 ATACs was more pronounced in PDX models with hemizygous loss of TP53 and POLR2A reflecting a 17p deletion. Safety profiling of an optimized anti-Her2 ATAC in cynomolgus monkeys revealed a good tolerability indicating a good therapeutic window for 17p deleted TNBC.

Conclusions:

Targeted cytotoxic drug delivery to HER2 positive cell lines was achieved by using anti-HER2 ATACs. The mode of action of the payload amanitin led to an efficient anti-tumor potential in vitro and in vivo with good tolerability in NHP studies. TNBC PDX models with HER2low expression were sensitive to ATAC treatment. Loss of POLR2A/chromosome 17p increased susceptibility to anti-HER2 ATAC making 17p del TNBC a suitable indication for optimized anti Her2 ATACs.

Citation Format: Christian Breunig, Anikó Pálfi, Michael Kulke, Christian Lutz, Christoph Müller, Torsten Hechler, Andreas Pahl. Preclinical evaluation of anti-HER2 Antibody Targeted Amanitin Conjugates (ATACs) on HER2low breast cancer with chromosome 17p deletion [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 237.

Abstract LB-106: Overcoming limitations of current Antibody-Drug Conjugates (ADCs) by a novel linker technology

We introduce a novel and versatile ADC-linker technology that is based on site-specific enzymatic payload conjugation to ‘off-the-shelf’ antibodies, i.e., without the need to reduce or engineer the antibody. The functionalization takes place site-specifically and stoichiometrically (drug-to-antibody ratio, DAR = 2.0) at the Fc-part of antibodies. The resulting ADCs show favorable biophysical properties such as high solubility and stability using different payloads. Additionally, initial ELISA findings show that our modification does not interfere with Fc-gamma receptor and FcRn binding. Importantly, our ADCs showed superior efficacy in different tumor animal models as compared to control Thiomab™ ADCs. Using native trastuzumab (non-engineered) as the targeting antibody and amanitin as payload, we generated within 36 hours highly homogeneous and pure ADCs with a well-defined DAR of 2.0 as confirmed by LC-MS. In in-vitro assays our ADCs demonstrated potent cytotoxicity in all tested cell-lines (SKBR-3, BT-474, JIMT-1, and NCI-N87) as compared to the control Thiomab™ ADCs, most strikingly for the JIMT-1 cell-line: EC50 of 0.15nM vs 2.5nM. In the mouse JIMT-1 tumor model, our anti-HER2 ADC was highly potent and resulted in complete tumor remission in all mice (10/10 mice) at a single dose of 2mg/kg. In contrast, the control Thiomab™-functionalized ADC showed tumor regrowth in 4 out of 10 animals, starting on day 50. The same high potency was observed for the NCI-N87 xenograft model at a dose of 3mg/kg in which tumor growth inhibition was significantly delayed versus the reference ADC (8/10 vs 4/10 animals alive on day 110). These encouraging results obtained so far indicate that our linker technology a) allows for fast (< 36 hours) and straightforward manufacturing of ADCs using different payloads without protein engineering efforts, b) results in ADCs with favorable biophysical properties and a clear defined drug-to-antibody ratio, and c) enables the generation of highly potent and stable, thus safer, next-generation ADCs.

Citation Format: Philipp Rene Spycher, Julia Carina Frei, Jöri Elias Wehrmüller, Isabella Attinger-toller, Dragan Grabulovski, Torsten Hechler, Michael Kulke, Andreas Pahl, Martin Behe, Roger Schibli. Overcoming limitations of current Antibody-Drug Conjugates (ADCs) by a novel linker technology [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 LB-106.

Amanitins and their development as a payload for antibody-drug conjugates

Amanitin-based ADCs represent a new class of ADCs using a novel mode of action. This payload introduces a novel mode of action into oncology therapy, the inhibition of RNA Polymerase II. The high potency of the toxin leads to highly efficacious ADCs. The development of the technology around this toxin will be described. These developments support the clinical development of amanitin-based ADCs by using a toxin with a new mode of action and with a favorable therapeutic index. HDP-101 is an Amanitin based ADC directed against BCMA and will be advancing to the clinical phase in 2019.

Abstract 740: Preclinical evaluation of an anti-PSMA antibody-targeted amanitin conjugate (ATAC)

Background:

ATACs (antibody-targeted Amanitin conjugates) comprise a new class of antibody-drug conjugates using Amanitin as toxic payload. Amanitin binds to the eukaryotic RNA pol II and thereby inhibits the cellular transcription process at very low concentrations. In the current study, in vitro and in vivo data of an ATAC targeting PSMA (prostate specific membrane antigen) are presented. PSMA is predominantly expressed on malignant prostate cells in prostate carcinoma and correlates with tumor progression. Hence it is considered an interesting target for Amanitin based ADCs.

Material and methods:

PSMA cell lines: MDA-PCA-2B, LnCap. PC3 cell line served as PSMA negative control.

Antibody: humanized anti-PSMA and cysteine engineered monoclonal antibody (Albert Ludwig University Freiburg, medical center; humanization at Lonza Group AG, derivatization and production at Heidelberg Pharma).

Toxic warhead: A cysteine reactive amanitin-linker was conjugated site-specifically to engineered cysteine residues of the anti-PSMA antibody yielding an ATAC with a DAR of 2.0.

Cell proliferation assay: Quantitative determination of cell viability was performed by CellTiter Glo 2.0 assay (Promega).

Animal models: Subcutaneous Mouse xenograft tumor models with PSMA-positive cell lines MDA-PCA-2B and LnCap were performed in single-dose and multiple-dosing experiments. Tolerability was assessed in mice and non-human primates (NHP).

Results:

The anti-PSMA ATAC showed in vitro cytotoxicity on PSMA+ cell lines in picomolar range, whereas no cytotoxic activity on PSMA- cells was observed.

In mouse xenograft models, the anti-PSMA ATAC caused dose-dependent tumor regression. Complete remission was achieved after a single i.v. dose of 4.0 mg/kg and after repeated i.v. doses of 2.0 mg/kg in s.c. xenografts.

Safety profiling in Cynomolgus monkeys revealed a good tolerability and therapeutic index after sequentially applied doses of 0.3, 1.0 and 3.0 mg/kg. Hematology and clinical chemistry parameters were unaffected except liver enzymes and LDH: A moderate and transient increase was observed. The half-life of the ATAC in serum was 7-10 days; the free toxin was detectable at levels close to the lower limit of quantification only (LLOQ = 1.2 nM).

Conclusions:

Targeted cytotoxic drug delivery to PSMA positive prostate cancer cell lines was achieved by using an anti-PSMA ATAC. The mode of action of the payload Amanitin led to an efficient anti-tumor potential in vitro and in vivo with good tolerability in NHP studies. The use of ATACs in the therapy of PSMA positive prostate cancer is a promising approach, especially by using a cytotoxic agent whose mode of action differs from other commonly used toxins.

Citation Format: Anikó Pálfi, Christian Breunig, Torsten Hechler, Christoph Müller, Christian Lutz, Andreas Pahl, Michael Kulke. Preclinical evaluation of an anti-PSMA antibody-targeted amanitin conjugate (ATAC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 740.

Abstract 735: SAR of amanitin and optimization of linker-amanitin derivatives for solid tumors

Background:

ATACs (Antibody Targeted Amanitin Conjugates) comprise a new class of antibody-drug conjugates using amanitin as toxic payload. Amanitin binds to the eukaryotic RNA pol II and thereby inhibits the cellular transcription process at very low concentrations. We accomplished the chemical synthesis of amanitin and were able to synthesize amanitin variants in order to optimize the toxin structure for different tumors and antibodies. We will present in vitro and in vivo data of eight different linker-amanitin constructs attached to three different antibodies targeting solid tumors.

Material and methods:

Cell lines: JIMT-1, SKBR-3, BT474 and NCI-N87 (used for anti-Her-2-ATACs); LnCap, 22RV1, MDA-PCa2b and C4.2 (used for anti-PSMA-ATACs); Raji, Raji Luc, Nalm-6 and MEC-2 (used for anti-CD19-ATACs)

Antibodies: Anti-Her-2 (cysteine engineered monoclonal antibody, Heidelberg Pharma); humanized anti-PSMA (Albert Ludwig University Freiburg, medical center; humanization at Lonza Group AG; cysteine engineered monoclonal antibody, Heidelberg Pharma); chimeric anti-CD19 (DKFZ Heidelberg, Germany; cysteine engineered monoclonal antibody, Heidelberg Pharma).

Toxic warhead: Cysteine reactive linker-amanitin constructs were synthesized at Heidelberg Pharma and conjugated site-specifically to the antibodies.

Cell proliferation assay: Quantitative determination of cell viability was performed by CellTiter Glo 2.0 assay (Promega).

Animal models: Subcutaneous Mouse xenograft tumor models (Her-2-, PSMA- and CD19-positive cell lines) were performed in single-dose experiments. Tolerability was assessed in mice and will be assessed in non-human primates (NHP).

Results:

Eight different amanitin-linker constructs were synthesized. They differed in the attachment site of the linker at the amanitin as well as in the toxin core structure. All ATACs showed in vitro cytotoxicity on target positive cell lines in the picomolar range.

In mouse xenograft models, ATACs with four of the eight linker-amanitin derivatives caused dose-dependent tumor regression and complete remission after a single i.v. dose of 2.0 mg/kg in s.c. xenografts irrespective of the antibody and target used. In contrast the other four linker-amanitin derivatives were only poorly effective in vivo while showing comparable in vitro activities. When comparing subcutaneous and intravenous xenograft models using the same cancer cell line, the different efficacy of the eight linker-amanitin variants was only detected in subcutaneous but not in intravenous xenografts. Mouse tolerability studies of ATACs showed a MTD of at least 10mg/kg for all linker-amanitin variants.

Conclusions:

Different efficacy of linker-amanitin derivatives with regard to mouse xenograft models was detected. An SAR profile of amanitin could be established which enabled the selection of optimized linker-amanitin variants for the use of ATACs in solid tumors.

Citation Format: Michael Kulke, Anikó Pálfi, Christoph Müller, Werner Simon, Susanne Werner-Simon, Christian Lutz, Torsten Hechler, Andreas Pahl. SAR of amanitin and optimization of linker-amanitin derivatives for solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 735.

Synthesis and biological evaluation of RGD and isoDGR peptidomimetic-α-amanitin conjugates for tumor-targeting

RGD-α-amanitin and isoDGR-α-amanitin conjugates were synthesized by joining integrin ligands to α-amanitin via various linkers and spacers. The conjugates were evaluated for their ability to inhibit biotinylated vitronectin binding to the purified α_Vβ₃ receptor, retaining good binding affinity, in the same nanomolar range as the free ligands. The antiproliferative activity of the conjugates was evaluated in three cell lines possessing different levels of α_Vβ₃ integrin expression: human glioblastoma U87 (α_Vβ₃+), human lung carcinoma A549 (α_Vβ₃−) and breast adenocarcinoma MDA-MB-468 (α_Vβ₃−). In the U87, in the MDA-MB-468, and partly in the A549 cancer cell lines, the cyclo[DKP-isoDGR]-α-amanitin conjugates bearing the lysosomally cleavable Val-Ala linker were found to be slightly more potent than α-amanitin. Apparently, for all these α-amanitin conjugates there is no correlation between the cytotoxicity and the expression of α_Vβ₃ integrin. To determine whether the increased cytotoxicity of the cyclo[DKP-isoDGR]-α-amanitin conjugates is governed by an integrin-mediated binding and internalization process, competition experiments were carried out in which the conjugates were tested with U87 (α_Vβ₃+, α_Vβ₅+, α_Vβ₆−, α₅β₁+) and MDA-MB-468 (α_Vβ₃−, α_Vβ₅+, α_Vβ₆+, α₅β₁−) cells in the presence of excess cilengitide, with the aim of blocking integrins on the cell surface. Using the MDA-MB-468 cell line, a fivefold increase of the IC₅₀ was observed for the conjugates in the presence of excess cilengitide, which is known to strongly bind not only α_Vβ₃, but also α_Vβ₅, α_Vβ₆, and α₅β₁. These data indicate that in this case the cyclo[DKP-isoDGR]-α-amanitin conjugates are possibly internalized by a process mediated by integrins different from α_Vβ₃ (e.g., α_Vβ₅).

Abstract 77: Preclinical evaluation of HDP-101, an anti-BCMA antibody-drug conjugate

Background:

ATACs (antibody-targeted Amanitin conjugates) comprise a new class of antibody-drug conjugates using amanitin as toxic payload. Amanitin binds to the eukaryotic RNA pol II and thereby inhibits the cellular transcription process at very low concentrations. In the current study, in vitro and in vivo data of new ATACs targeting BCMA (B Cell Maturation Antigen, also known as CD269) are presented. BCMA is selectively expressed on malignant plasma cells like in multiple myeloma (MM) and hence considered an ideal target for Amanitin based ADCs.

Material and methods:

MM cell lines: NCI-H929, MM.1S Luc (stable luciferase transfected) and CCRF-CEM (BCMA negative).

Antibody: anti-BCMA Thiomab (Max Delbrück Centrum, Berlin; derivatization and production at Heidelberg Pharma).

Synthesis of HDP-101: Maleimide amanitin compounds were conjugated to substituted cysteine residues of the anti-BCMA Thiomab.

Cell proliferation assay: Quantitative determination of cytotoxicity was performed by CellTiter Glo 2.0 assay (Promega) or WST.1 assay (Roche).

Animal models: Subcutaneous and metastatic mouse xenograft tumor models with MM cell lines NCI-H929 and MM.1S Luc were performed in single-dose and multiple-dosing experiments. Tolerability was assessed in mice and nonhuman primates (NHP).

Results:

HDP-101 showed in vitro cytotoxicity on BCMA+ cell lines in picomolar range, whereas no cytotoxic activity on BCMA- cells was observed.

In mouse xenograft models, HDP-101 caused dose-dependent tumor regression and complete remission after a single i.v. dose of 2.0 mg/kg and 4.0 mg/kg in s.c. xenografts and after single i.v. doses from 0.1 mg/kg to 2.0 mg/kg in disseminating xenografts.

Safety profiling in Cynomolgus monkeys revealed a good tolerability and therapeutic index after sequentially applied doses of 0.3, 1.0, and multiple dose application of 4 x 3.0 mg/kg. Hematology and clinical chemistry parameters were unaffected except liver enzymes and LDH: A mild to moderate and transient increase was observed. The half-life of the ADC in serum was 7-9 days; the free toxin was detectable at levels close to the lower limit of quantification only (LLOQ = 1.2nM).

Conclusions:

Targeted cytotoxic drug delivery to BCMA positive MM cell lines was achieved by using HDP-101, an anti-BCMA-ATAC. The mode of action of the payload Amanitin led to an efficient anti-tumor potential in vitro and in vivo with good tolerability in NHP studies. Using ADCs in the therapy of multiple myeloma is a promising approach, especially by using a cytotoxic agent whose mode of action differs from other commonly used toxins, like ATACs. First-in-human trial is expected to start in 2018.

Citation Format: Torsten Hechler, Aniko Palfi, Christoph Müller, Christian Lutz, Andreas Pahl, Michael Kulke. Preclinical evaluation of HDP-101, an anti-BCMA antibody-drug conjugate [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 77. doi:10.1158/1538-7445.AM2017-77

Abstract 2973: CD269 - A promising target for amanitin based ADCs

Antitumor activity of monoclonal antibodies can be dramatically enhanced by conjugation to toxic small molecules. Beside the recent approval of Kadcyla (T-DM1) and Adcetris (SGN-35) more than 30 antibody-drug conjugates (ADC) have entered clinical trials, promising to strengthen the therapeutic capabilities for cancer treatment in the next decade. Surprisingly most ADCs are based on one of few toxic compounds only and on an even smaller number of toxicity mechanisms: Most antibodies are coupled to the microtubuli-targeting auristatins and maytansines. Toxins that operate through such a mechanism could suffer from limited activity in different cancer indications and in cells expressing resistance mechanisms. Accordingly the use of new drugs that function via alternative toxicity mechanisms could enhance the therapeutic potential of ADCs. Heidelberg Pharma focuses on Amanitin, the most well-known toxin of the amatoxin family. Amanitin binds to the eukaryotic RNA pol II and thereby inhibits the cellular transcription at very low concentrations.

In the current study, in vitro and in vivo Data of Amanitin-ADCs targeting CD269 (B cell maturation antigen) are presented. CD269 is expressed on cells of the B cell lineage, predominantly on plasma blasts and plasma cells. It is not expressed on naïve B cells, germinal center B cells and memory B-cells (Darce et al. (2007) J Immunol 179:7276-7286). CD269 is highly expressed on malignant plasma cells like multiple myeloma, a B cell non Hodgkin lymphoma of the bone marrow (Novak et al. (2004) Blood 103:689-94). Since multiple myeloma is a usually incurable malignancy of plasma cells, new therapies are urgently needed. Using ADCs in the cure of multiple myeloma could be a promising approach, especially by using a toxin whose mode of action was not applied before, like amanitin based ADCs.

In vitro data of anti-CD269-amanitin ADC showed cytotoxicity on CD269 positive cell lines in picomolar range, while up to micromolar concentrations, no cytotoxic activity on CD269 negative cells was observed. In mouse xenograft models, anti-CD269-amanitin showed clear anti-tumorigenic potential. A comprehensive data package will be presented.

Citation Format: Aniko Palfi, Torsten Hechler, Christoph Mueller, Andreas Pahl, Michael Kulke. CD269 - A promising target for amanitin based ADCs. [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 2973.

Abstract A69: A novel mechanism mediates drug resistance in the exocrine-like pancreatic ductal adenocarcinoma (PDAC) subtype

PDAC is a highly aggressive disease with dismal prognosis [1, 2]. Despite extensive research and the discovery of several drug candidates, little progress has been reported since the approval of gemcitabine and erlotinib [1]. Moreover, recent trials with targeted therapies have shown only limited or no benefit [1, 2]. For a number of other carcinomas, tumor subclasses have been uncovered that allow the use of targeted therapies. The mutational landscape of PDAC is complex and heterogeneous, raising the question whether subclasses also exist in PDAC [3]. Collisson et al. described three PDAC subtypes that were identified based on their gene-expression profiles: The classical, the quasi-mesenchymal and the exocrine-like subtype [4]. However, not all subtypes could be identified in the previously available model systems. We have established a novel patient-derived model system that allows the analysis of these three human PDAC subtypes in vitro and in vivo. Hence, we provide a systematic workflow to propagate human PDAC in orthotopic xenografts and to derive tumor-initiating primary cell lines of all three PDAC subtypes. HNF-1 and Keratin 81 were identified as markers for subtype stratification by immunohistochemistry. Application of this two-marker set on a 258 large patient cohort confirmed a predominantly non-overlapping staining and revealed a significant difference in overall survival across the three subtypes. Furthermore, a drug screen uncovered subtype-specific drug sensitivities towards a number of drugs, including gemcitabine and dasatinib. Notably, the exocrine-like subtype was resistant towards all compounds tested. Thus, we aimed to identify the underlying cause of the observed drug resistance. Molecular analysis including gene set enrichment analysis (GSEA) allowed us to identify a putative novel mechanism of drug resistance. Analysis by qRT-PCR and Western blot demonstrated the enhanced expression of several genes mediating this mechanism particularly in the exocrine-like subtype in vitro and in vivo. These findings led to the identification of a novel protein target central to this mechanism. Additionally, retrospective immunohistochemical analysis of a large patient cohort confirmed that this target is predominantly found in those patient tumors classified as exocrine-like. Hence, we hypothesized that the observed strong activation of this mechanism in the exocrine-like PDAC subtype could be responsible for the drug resistance observed in this subclass. In line with this, functional inhibition of this mechanism resulted in increased drug sensitivity in the exocrine-like subtype. Hence, our findings may ultimately advance personalized treatment by applying novel marker-based patient selection strategies in combination with tailored drug use, a strategy which will be presented in more detail at the conference.

[1] Hidalgo, M. Pancreatic cancer. The New England journal of medicine. 362, 1605-1617, doi:10.1056/NEJMra0901557 (2010).

[2] Vincent, A., Herman, J., Schulick, R., Hruban, R. H. & Goggins, M. Pancreatic cancer. Lancet. 378, 607-620, doi:10.1016/S0140-6736(10)62307-0 (2011).

[3] Jones, S. et al. Core signalling pathways in human pancreatic cancers revealed by global genomic analyses. Science. 321, 1801-1806, doi:10.1126/science.1164368 (2008).

[4] Collisson, E. A. et al. Subtypes of pancreatic ductal adenocarcinoma and their differing responses to therapy. Nature medicine. 17, 500-503, doi:10.1038/nm.2344 (2011).

Citation Format: Elisa M. Noll, Christian Eisen, Elisa Espinet, Vanessa Vogel, Corinna Klein, Albrecht Stenzinger, Franziska Zickgraf, Peter Neuhaus, Marcus Bahra, Bruno V. Sinn, Christian Lutz, Michael Kulke, Andreas Pahl, Nathalia A. Giese, Oliver Strobel, Jens Werner, Wilko Weichert, Andreas Trumpp, Martin R. Sprick. A novel mechanism mediates drug resistance in the exocrine-like pancreatic ductal adenocarcinoma (PDAC) subtype. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A69.

TP53 loss creates therapeutic vulnerability in colorectal cancer

TP53, a well-known tumour suppressor gene that encodes p53, is frequently inactivated by mutation or deletion in most human tumours. A tremendous effort has been made to restore p53 activity in cancer therapies. However, no effective p53-based therapy has been successfully translated into clinical cancer treatment owing to the complexity of p53 signalling. Here we demonstrate that genomic deletion of TP53 frequently encompasses essential neighbouring genes, rendering cancer cells with hemizygous TP53 deletion vulnerable to further suppression of such genes. POLR2A is identified as such a gene that is almost always co-deleted with TP53 in human cancers. It encodes the largest and catalytic subunit of the RNA polymerase II complex, which is specifically inhibited by α-amanitin. Our analysis of The Cancer Genome Atlas (TCGA) and Cancer Cell Line Encyclopedia (CCLE) databases reveals that POLR2A expression levels are tightly correlated with its gene copy numbers in human colorectal cancer. Suppression of POLR2A with α-amanitin or small interfering RNAs selectively inhibits the proliferation, survival and tumorigenic potential of colorectal cancer cells with hemizygous TP53 loss in a p53-independent manner. Previous clinical applications of α-amanitin have been limited owing to its liver toxicity. However, we found that α-amanitin-based antibody-drug conjugates are highly effective therapeutic agents with reduced toxicity. Here we show that low doses of α-amanitin-conjugated anti-epithelial cell adhesion molecule (EpCAM) antibody lead to complete tumour regression in mouse models of human colorectal cancer with hemizygous deletion of POLR2A. We anticipate that inhibiting POLR2A will be a new therapeutic approach for human cancers containing such common genomic alterations.

Efficacy of drugs used in the treatment of IBD and combinations thereof in acute DSS-induced colitis in mice

AIMS

Although acute dextran sodium sulphate (DSS)-induced colitis in mice is frequently used as a preclinical model for testing drugs involved in inflammatory bowel disease (IBD), only limited data is available that compares the efficacy of established drug treatments and combinations employed in IBD. We have therefore compared the efficacy of aminosalicylates (mesalazine, olsalazine), corticosteroids (budesonide), thiopurines (6-thioguanine (6-TG)) and cyclosporine A (CsA) and combinations thereof as well as the EP4 agonist AGN205203 in the acute DSS-colitis model.

MAIN METHODS

Female BALB/c mice were challenged with 4% DSS in drinking water for 7 days to induce colitis and treated daily with different drugs/combinations orally. Disease scores (diarrhoea, bleeding, disease activity index), systemic (body weight loss, serum amyloid A levels) and colonic (myeloperoxidase activity, length and histopathology) inflammation parameters were analysed.

KEY FINDINGS

Mesalazine, olsalazine (100mg/kg) and budesonide (0.5mg/kg) were only weakly active or even worsened colitis. 6-TG dose-dependently reduced systemic and colonic inflammation parameters with estimated ED50 values between 0.5-4 mg/kg. CsA (10, 25 and 50mg/kg) dose-dependently reduced colitis with high efficacy on systemic inflammation. A combination of CsA 25mg/kg+olsalazine 100mg/kg produced a more pronounced anti-inflammatory effect than the compounds given alone. AGN205203 (3, 10 and 30 mg/kg BID) was the most efficacious compound and almost completely inhibited colitis.

SIGNIFICANCE

6-TG and CsA are suitable reference compounds in the DSS mouse model. CsA+olsalazine, as a combination, was more efficacious than the compounds given alone, supporting combination treatments in IBD.

Regulation of MMP-9 by a WIN-binding site in the monocyte-macrophage system independent from cannabinoid receptors

The cannabinoid system is known to be involved in the regulation of inflammatory processes. Therefore, drugs targeting cannabinoid receptors are considered as candidates for anti-inflammatory and tissue protective therapy. We demonstrated that the prototypical cannabinoid agonist R(+)WIN55,212-2 (WIN) reduced the secretion of matrix metalloproteinase-9 (MMP-9) in a murine model of cigarette-smoke induced lung inflammation. In experiments using primary cells and cell lines of the monocyte-macrophage-system we found that binding of the cannabinoid-receptor agonist WIN to a stereo-selective, specific binding site in cells of the monocyte-macrophage-system induced a significant down-regulation of MMP-9 secretion and disturbance of intracellular processing, which subsequently down-regulated MMP-9 mRNA expression via a ERK1/2-phosphorylation-dependent pathway. Surprisingly, the anti-inflammatory effect was independent from classical cannabinoid receptors. Our experiments supposed an involvement of TRPV1, but other yet unidentified sites are also possible. We conclude that cannabinoid-induced control of MMP-9 in the monocyte-macrophage system via a cannabinoid-receptor independent pathway represents a general option for tissue protection during inflammation, such as during lung inflammation and other diseases associated with inflammatory tissue damage.

Desmoglein 3-specific T regulatory 1 cells consist of two subpopulations with differential expression of the transcription factor Foxp3

Pemphigus vulgaris (PV) is an autoimmune bullous skin disorder associated with autoantibodies against desmoglein (Dsg) 3. An imbalance of type 1 regulatory T (Tr1) cells and T helper type 2 (Th2) cells specific for Dsg3 may be critical for the loss of tolerance against Dsg3 in PV. Within the population of Dsg3-responsive, interleukin (IL)-10-secreting Tr1 cell clones, two major subpopulations were identified and sorted by fluorescence-activated cell sorting (FACS) based on their size and granularity. Upon in vitro culture, the larger subpopulation differentiated back into the two former subpopulations of the Tr1 cell clones, while the smaller subpopulation died within 2 weeks. The smaller subpopulation of the Tr1 cell clones was characterized by the expression of Foxp3, the secretion of IL-10, transforming growth factor (TGF)-beta and IL-5 upon stimulation with Dsg3, a proliferative response to IL-2 but not to Dsg3 or mitogenic stimuli, and an inhibitory effect on the proliferative response of Dsg3-responsive Th clones in a Dsg3-specific manner. In contrast, the larger subpopulation showed a Th-like phenotype, lacking Foxp3, cytotoxic T-lymphocyte antigen 4 (CTLA4) and glucocorticoid-induced tumour necrosis factor receptor (GITR) expression and IL-2 secretion, and did not mount a proliferative response to Dsg3 and mitogenic stimuli. The two Tr1 subpopulations showed expression of identical T-cell receptor (TCR) V beta chains which varied among the PV patients studied. Upon inhibition of Foxp3, the smaller Tr1 subpopulation developed a proliferate response to Dsg3 and mitogenic stimuli, no longer suppressed Dsg3-specific Th cells, lost expression of GITR and CTLA4 and secreted IL-2. Thus, our observations suggest a distinct relationship between Dsg3-specific Tr1 and Th-like cells which may be critical for the continuous generation and survival of Dsg3-specific Tr1 cells.

Cytochrome P450 2C19 681G>A polymorphism and high on-clopidogrel platelet reactivity associated with adverse 1-year clinical outcome of elective percutaneous coronary intervention with drug-eluting or bare-metal stents

OBJECTIVES

We investigated whether the loss of function CYP2C19 681G>A *2 polymorphism is associated with high (>14%) residual platelet aggregation (RPA) on clopidogrel and whether high on-clopidogrel RPA impacts clinical outcome after elective coronary stent placement.

BACKGROUND

The cytochrome P450 (CYP)-dependent conversion of clopidogrel to its active metabolite may contribute to the variability in antiplatelet effect of clopidogrel.

METHODS

The study included 797 consecutive patients undergoing percutaneous coronary intervention, who were followed-up for 1 year. Adenosine-diphosphate-induced (5 mumol/l) RPA was assessed after a 600-mg loading dose and after the first 75-mg maintenance dose of clopidogrel before discharge. CYP2C19 genotype was analyzed by real-time polymerase chain reaction.

RESULTS

Of the patients included, 552 (69.3%) were CYP2C19 wild-type homozygotes (*1/*1) and 245 (30.7%) carried at least one *2 allele. Residual platelet aggregation at baseline did not differ significantly between genotypes. On clopidogrel, RPA was significantly (p < 0.001) higher in *2 carriers than in wild-type homozygotes (23.0% [interquartile range (IQR) 8.0% to 38.0%] vs. 11.0% [IQR 3.0% to 28.0%] after loading; 11.0% [IQR 5.0% to 22.0%] vs. 7.0% [IQR 3.0% to 14.0%] at pre-discharge). Between *2 carriers and wild-type homozygotes, we found significant (p < 0.001) differences in the proportion of patients with RPA >14%, both after loading (62.4% vs. 43.4%) and at pre-discharge (41.3% vs. 22.5%). Residual platelet aggregation >14% at pre-discharge incurred a 3.0-fold increase (95% confidence interval 1.4 to 6.8; p = 0.004) in the 1-year incidence of death and myocardial infarction.

CONCLUSIONS

Patients carrying at least one CYP2C19*2 allele are more prone to high-on clopidogrel platelet reactivity, which is associated with poor clinical outcome after coronary stent placement (Effect of Clopidogrel Loading and Risk of PCI [EXCELSIOR]; NCT00457236).

Preclinical modelling using nasal epithelial cells for the evaluation of herbal extracts for the treatment of upper airway diseases

The epithelium constitutes the interface between the internal milieu and the external environment, and the nasal epithelium is the initial point of contact for respiratory viruses, airborne allergens and environmental pollutants. The major function of the nasal epithelium was regarded to be primarily that of a physical barrier, but recent studies clearly indicate that its cells are metabolically very active with the capacity to modulate a variety of inflammatory processes through the action of an array of receptor-mediated events. This review summarizes the current view of the active role of the nasal epithelium in the inflammation of the upper airways and its possible modulation by herbal extracts to treat diseases of the upper airways such as common cold and sinusitis.

Prospective use of CYP pharmacogenetics and medication analysis to facilitate improved therapy - a pilot study

OBJECTIVES

To assess the efficacy of cytochrome P450 (CYP) pharmacogenetic testing and medication interaction analysis in a controlled environment for reduction of events, stays in hospital, extra care and required extra doctors visits to the patients.

METHODS

A prospective cohort study of 28 patients in a geriatric care facility with multimedication and at least one report of an event was performed over a period of 7 months. In the first phase of the study the patients were closely monitored twice a day by the care staff, recording all potential events, regardless of association with the indication or not, requirement for extra care, requirement for an unplanned site visit from a physician and days in hospital. In a 1-month period, the patients were genotyped for the cytochromes CYP2C9, CYP2C19 and CYP2D6, and their medication analyzed for interactions, using a proprietary computer program. Recommendations for medication change based upon genetics and/or medication interaction analysis were made to the care physicians. In a second 3-month phase the patients were monitored as in Phase I. The data comparing Phase I with Phase II was analyzed using two way ANOVA.

RESULTS

Of the 28 patients in the study in both phases, 16 (55%) had genetic and/or medication interaction problems that required change of medication. A total of 11 out of 16 (69%) of the patients did have their medication altered by the care physician. Of the 11 patients, five (45%) demonstrated some betterment in the number of reported events after alteration of their medication. Of these five patients, three had improvements when their medication was altered for their genetics. A further three (one patient had improvements due to both effects) had improvements when their medication was altered after a medication interaction analysis.

CONCLUSION

Although an exploratory pilot study, this cohort study shows the possibilities and potential of pharmacogenetic testing for CYP alterations combined with medication interaction analysis of patients in a geriatric care facility.

The association of ABCB1 polymorphisms and elevated serum digitoxin concentrations in geriatric patients

OBJECTIVE

Digitoxin is a known substrate of the efflux pump P-glycoprotein (gene name: ABCB1). P-glycoprotein expression was shown to be modulated by single nucleotide polymorphisms in the ABCB1 gene, but it remains unclear whether these polymorphisms influence digitoxin blood levels. Our objective was to examine the association of ABCB1 C3435T genotype and elevated serum digitoxin concentrations (SDC) in a cohort of 77 geriatric patients consecutively admitted to a geriatric department over a 12-month period.

METHODS

The impact of ABCB1 3435 CC, CT, and TT genotypes on SDC and SDC normalized for daily digitoxin dosage and body weight was assessed by multivariate regression analysis.

RESULTS

Among participants, 18 (23%) had the CC, 36 (47%) the CT, and 23 (30%) the TT genotype. Adjusting for relevant covariates, no significant association of ABCB1 C3435T genotype and SDC or normalized SDC was detected. Mean SDC was 22.4 ng/ml (95% CI 18.9-25.9) for the TT, 21.8 ng/ml (95% CI 18.1-25.5) for the CT, and 25.7 ng/ml (95% CI 20.6-30.8) for the CC genotype. The means for normalized SDC were 5.2 kg.l(-1) (95% CI 4.3-6.1) for the TT, 6.1 kg.l(-1) (95% CI 4.7-7.5) for the CT, and 6.2 kg.l(-1) (95% CI 4.6-7.7) for the CC genotype.

CONCLUSION

In this sample of frail geriatric patients, the impact of ABCB1 C3435T genotype on serum digitoxin concentration was not of major relevance. Regular monitoring of digitoxin blood levels and surveillance of appropriate drug use remain the best ways to prevent digitoxin intoxications in the elderly.

Cytokine profiles of cord and adult blood leukocytes: differences in expression are due to differences in expression and activation of transcription factors

BACKGROUND

Stem cell transplantation as therapy for hematological disorders is often hampered by severe graft-versus-host-disease. This may be reduced by umbilical cord blood transplantation, an effect that has been attributed to qualitative differences between neonatal and adult T cells. We compared levels of secreted proteins and cytokine mRNA induced in cord blood leukocytes (CBL) and adult blood leukocytes (ABL) by various stimuli.

RESULTS

While interleukin-2 (IL-2) levels were similar in CBL and ABL, there was less induction of the Th1 cytokine interferon-gamma in CBL. Production of the Th2 cytokines IL-4, IL-5, and IL-13 and the hematopoietic cytokine IL-3 was much lower in CBL versus ABL after T-cell receptor-mediated stimulation, whereas production of GM-CSF was comparable in the 2 cell types. The lower levels of Th1 and Th2 cytokines were maintained in CBL during a 4-day time-course study, while after 12 hours IL-3 and GM-CSF reached in CBL levels similar to those in ABL. For all cytokines except IFN gamma, the IC50 values for inhibition by cyclosporin A were similar in ABL and CBL. In contrast, there was less expression and activation of transcription factors in CBL. Activation of NF-kappaB by TPA/ionomycin was detected in ABL but not CBL. Furthermore, there was less expression of the Th subset-specific transcription factors T-bet and c-maf in CBL versus ABL, whereas GATA-3 expression was similar. Expression of T-bet and c-maf correlated with expression of the Th1 and Th2 cytokines, respectively. Time course experiments revealed that T-bet expression was stimulated in both cell types, whereas c-maf and GATA-3 were induced only in ABL.

CONCLUSION

The diminished capability of CBL to synthesize cytokines is probably due to decreased activation of NF-kappaB, whereas differences in Th subsets are due to differences in regulation of Th lineage-specific transcriptions factors. We propose that the reduced incidence and severity of GvHD after allogeneic transplantation of umbilical CB cells is due to lesser activation of specific transcription factors and a subsequent reduction in production of certain cytokines.

MDR1 genotype-dependent regulation of the aldosterone system in humans

OBJECTIVE

Aldosterone plays a major role in the development of both hypertension and heart failure. As aldosterone is a substrate of the ABCB1 (P-glycoprotein) efflux transporter, whose expression and activity has been shown to be linked to the ABCB1 3435C-->T polymorphism, we tested the impact of the ABCB1 3435C-->T polymorphism on aldosterone disposition, blood pressure, cardiac structure, and kidney function.

METHODS

A homogenous group of 116 young, white male Caucasian individuals with normal or mildlyto moderately elevated, but never treated blood pressure was included. Blood pressure was compared between individuals with ABCB1 3435 CC, CT, and TT genotypes. Moreover, genotype-dependent differences in basal and angiotensin II-stimulated serum aldosterone, cardiac structure, and kidney function were evaluated.

RESULTS

Of the 116 volunteers, 35 had the CC, 51 the CT and 30 the TT genotype. At baseline, no significant genotype-dependent differences in serum aldosterone were observed. After infusion of angiotensin II, the increase in aldosterone serum concentration was significantly higher in the TT group than that in the CT and CC groups (CC +11+/-35, CT +18+/-48, TT +45+/-50 pg/ml, P=0.012). Systolic and diastolic blood pressure, left ventricular structure, and function and baseline renal function were not significantly different. After additional oral sodium load (5 g/day over 1 week) urinary sodium excretion was found to be increased in individuals with the CC or CT genotype only but not in those with the TT genotype (CC +71+/-83, CT +52+/-114, TT -11+/-98 mmol/day, P=0.005).

CONCLUSION

The present study demonstrates that the ABCB1 3435 genotype affects angiotensin II-stimulated serum aldosterone levels and salt-stimulated urinary sodium excretion. Although blood pressure and cardiac structure were unchanged in this young study population, our findings indicate a new link between MDR1 genotype and the aldosterone system in humans.

Pharmacogenomics of asthma

Patient response to asthma therapy is consistently observed to be heterogeneous. Pharmacogenomics is the study of inherited differences in interindividual drug disposition and effects, with the goal of selecting the optimal drug therapy and dosage for each patient. This review will cover selected examples of gene polymorphisms that influence the outcome of asthma therapy, and whole-genome expression studies using microarray technology that have shown tremendous potential for benefiting asthma pharmacogenomics. The utility of the mouse as an experimental system for pharmacogenomic discovery will also be discussed in the context of asthma therapy.

Lipopolysaccharide-induced lung inflammation is inhibited by neutralization of GM-CSF

Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the pathogenesis of acute and chronic lung disease as a major regulator governing the functions of granulocyte and macrophage lineage populations. Chronic obstructive pulmonary disease (COPD) is a disease characterized by lung inflammation with accumulation of neutrophils and increased levels of pro-inflammatory cytokines including GM-CSF in the patient's lungs. We used intranasal administration of lipopolysaccharide (LPS) to mice to induce a disease that resembles COPD with pulmonary inflammation, neutrophil recruitment and release of pro-inflammatory mediators in the bronchoalveolar lavage fluid of the diseased mice. 2 h prior to LPS administration, mice were systemically treated with the murine GM-CSF neutralizing antibody mAb 22E9 per intraperitoneal injection. Intranasal challenge with LPS-induced an increase of total cell number and of neutrophils in the bronchoalveolar lavage fluid. Elevated levels of tumor necrosis factor alpha (TNF-alpha), keratinocyte cytokine and macrophage inflammatory protein-2 (MIP-2) were also observed at this time point. GM-CSF was no longer detectable in bronchoalveolar lavage fluid at 24 h due to its early expression with a peak reached 6 h after LPS challenge. Pretreatment of mice with GM-CSF neutralizing antibody dose-dependently inhibited the accumulation of neutrophils and reduced TNF-alpha and MIP-2 protein levels in bronchoalveolar lavage fluid. These data suggest that neutralization of GM-CSF may represent a novel treatment modality for lung inflammation and in particular for COPD.

Are there any realistic chances to develop new drugs for asthma?

Asthma bronchiale, an inflammatory airway disease, imposes a significant health care problem worldwide. It is characterized by three critical phenotypic traits: intermittent and reversible bronchoconstriction, bronchial hyperresponsiveness and airway inflammation. Conventional therapy basically consists of beta(2)-adrenoceptor agonists in combination with glucocorticoids. Nevertheless, there is an urgent need for novel therapies, both for patients with uncontrollable disease symptoms and for those suffering from glucocorticoid-insensitive asthma. Monotherapy seems to be relatively ineffective against this complex and multifaceted disease, which is evident by the variety of disappointing treatment strategies. Thus, we should instead concentrate on multiple target strategies, such as novel and more potent glucocorticoids or phosphodiesterase type 4 (PDE4) inhibitors with isozyme selectivity. In addition, an examination of the application method should not be neglected, with emphasis on inhalative approaches. To summarize, research into asthma's pathophysiology is of critical importance, concentrating on human-relevant targets and conducting preliminary studies. With these imperatives in mind, we can hope to better manage this multifactor disease in the near future.

Synergistic effects of the anti-cholinergic R,R-glycopyrrolate with anti-inflammatory drugs

Currently, much effort is geared towards developing therapies that impact on the inflammation in respiratory diseases such as asthma and COPD, assuming that this will improve disease pathology. R,R-Glycopyrrolate, a quaternary ammonium compound, is a muscarinic receptor antagonist with the potential to be used as a long-acting bronchodilator in patients with asthma and COPD. In this study we evaluated whether the combination of R,R-glycopyrrolate with known anti-inflammatory drugs results in synergistic effects. Human primary monocytes were used as an in vitro model system. M3, M4, M1 and M2 receptors were expressed in these cells in descending order. The combinatory effects of the drugs on the release of TNF-alpha after lipopolysaccharide stimulation were analyzed. R,R-Glycopyrrolate alone did not affect LPS induced TNF-alpha release. The PDE4 inhibitor rolipram dose dependently inhibited the TNF-alpha release. Maximum inhibition was around 70%. The IC(35) for rolipram was 68.9+/-15.2 nM. The simultaneous administration of 10 microM R,R-glycopyrrolate reduced the IC(35) to 1.70+/-1.18 nM. The anti-histamine azelastine inhibited TNF-alpha release dose dependently. The simultaneous administration of R,R-glycopyrrolate did not influence the action of azelastine. The corticosteroid budesonide inhibited the TNF-alpha release dose dependently with an IC(50) of 0.55+/-0.13 nM. The simultaneous administration of 10 microM R,R-glycopyrrolate reduced the IC(50) to 0.13+/-0.03 nM. Finally, R,R-glycopyrrolate was most effective in the triple combination with budesonide and rolipram in the reduction of TNF-alpha release. In conclusion, R,R-glycopyrrolate acts synergistically with the PDE4 inhibitor rolipram and the steroid budesonide in inhibiting inflammatory mediators.