Magali Guffroy

Biological Qualification of Biomarkers of Chemical-Induced Renal Toxicity in Two Strains of Male Rat

This study reports the evaluation of four urinary biomarkers of renal toxicity, α-glutathione-S-transferase (α-GST), μ-GST, clusterin, and renal papillary antigen-1 (RPA-1), in male Sprague-Dawley and Han-Wistar rats given cisplatin, gentamicin, or N-phenylanthranilic acid (NPAA). Kidney injury was diagnosed histopathologically, according to site/nature of renal injury, and graded for severity. The area under the receiver operating characteristic (ROC) curve was used to compare the diagnostic accuracy of each exploratory renal biomarker with traditional indicators of renal function and injury (blood urea nitrogen [BUN], serum creatinine [sCr] as well as urinary N-acetyl-β-D-glucosaminidase [NAG] and protein). These analyses showed that increased urinary α-GST was superior to BUN, sCr, and NAG for diagnosis of proximal tubular (PT) degeneration/necrosis. Paradoxically, urinary α-GST was decreased in the presence of collecting duct (CD) injury without PT injury (NPAA administration). RPA-1 demonstrated high specificity for CD injury, superior to all of the reference biomarkers. The clusterin response correlated well with tubular injury, whatever the location, particularly when regeneration was present (superior to all of the reference markers for cortical tubular regeneration). There was no conclusive evidence for the diagnostic utility of μ-GST. The data were submitted for qualification review by the European Medicines Agency and the US Food and Drug Administration. Both agencies concluded that the data justified the qualification of RPA-1 and increased the level of evidence for, and clarified the context of use of, the previously qualified clusterin for use in male rats. These biomarkers can be used in conjunction with traditional clinical chemistry markers and histopathology in Good Laboratory Practice rodent toxicology studies used to support renal safety studies in clinical trials. Qualification of α-GST must await further explanation of the differences in response to PT and CD injury.

A PTK7-targeted antibody-drug conjugate reduces tumor-initiating cells and induces sustained tumor regressions

PTK7 is a tumor-initiating cell antigen, which can be targeted with an antibody-drug conjugate to confer sustained tumor regressions. Initiating an antitumor attack Cancer is notorious for relapsing after treatment, making it difficult to eradicate from a patient’s body. Such relapses are driven by tumor-initiating cells, a type of stem cells that give rise to tumors. Damelin et al. determined that a protein called PTK7 is frequently present on tumor-initiating cells and developed an antibody-drug conjugate for targeting it. The authors demonstrated the effectiveness of this therapy in mouse models of several tumor types and confirmed that it reduces tumor-initiating cells and outperforms standard chemotherapy. The antibody-drug conjugate also had some unexpected benefits, reducing tumor angiogenesis and promoting antitumor immunity, all of which may contribute to its effectiveness. Disease relapse after treatment is common in triple-negative breast cancer (TNBC), ovarian cancer (OVCA), and non–small cell lung cancer (NSCLC). Therapies that target tumor-initiating cells (TICs) should improve patient survival by eliminating the cells that can drive tumor recurrence and metastasis. We demonstrate that protein tyrosine kinase 7 (PTK7), a highly conserved but catalytically inactive receptor tyrosine kinase in the Wnt signaling pathway, is enriched on TICs in low-passage TNBC, OVCA, and NSCLC patient–derived xenografts (PDXs). To deliver a potent anticancer drug to PTK7-expressing TICs, we generated a targeted antibody-drug conjugate (ADC) composed of a humanized anti-PTK7 monoclonal antibody, a cleavable valine-citrulline–based linker, and Aur0101, an auristatin microtubule inhibitor. The PTK7-targeted ADC induced sustained tumor regressions and outperformed standard-of-care chemotherapy. Moreover, the ADC specifically reduced the frequency of TICs, as determined by serial transplantation experiments. In addition to reducing the TIC frequency, the PTK7-targeted ADC may have additional antitumor mechanisms of action, including the inhibition of angiogenesis and the stimulation of immune cells. Together, these preclinical data demonstrate the potential for the PTK7-targeted ADC to improve the long-term survival of cancer patients.

Immunohistochemical Identification of Kidney Nephron Segments in the Dog, Rat, Mouse, and Cynomolgus Monkey

Kidney is a major target organ in preclinical studies. In recent years, intense research has been undertaken to characterize novel renal toxicity biomarkers. In this context, we studied nephron segment specific antibodies against aquaporin-1 (AQP-1), α-glutathione-S-transferase (alpha-GST), Tamm-Horsfall protein (TH), calbindin-D28K (CalD), and aquaporin-2 (AQP-2), using an immunoperoxidase method on formalin-fixed paraffin-embedded kidney tissues of dogs, rats, mice, and Cynomolgus monkeys. AQP-1 was specific for proximal tubules and thin descending limbs of Henle’s loops and AQP-2 for connecting and collecting ducts in dogs, rats, mice, and Cynomolgus monkeys. Alpha-GST stained the straight part of proximal tubules in dogs and proximal convoluted tubule and straight part of proximal tubules in rats. TH was specific for thick ascending limbs of Henle’s loops in mice, rats, dogs, and Cynomolgus monkeys and stained additionally scattered cells in cortical connecting/collecting ducts of dogs. CalD was found in distal convoluted tubules and cortical connecting and collecting ducts of dogs, rats, and mice and in distal convoluted tubules, connecting ducts, and cortical and medullary collecting ducts of Cynomolgus monkey. This panel of antibodies may be a helpful tool to identify renal tubules by light microscopy in preclinical studies and to validate new biomarkers of renal toxicity.

Normal Ranges and Variability of Novel Urinary Renal Biomarkers in Sprague-Dawley Rats Comparison of Constitutive Values between Males and Females and across Assay Platforms

Differences were examined between male and female Sprague-Dawley rats in basal levels of a wide range of urinary biomarkers, including 7 recently qualified biomarkers. The data were generated from urine samples collected on 3 occasions from untreated rats included in a study of the effect of gentamicin nephrotoxicity on urinary renal biomarkers, reported in a companion article in this journal (Gautier et al. 2014). The performance of multiple assays (9 singleplex assays and 2 multiplex platforms from Rules Based Medicine [RBM] and Meso Scale Discovery [MSD]) was evaluated, and normal ranges and variability estimates were derived. While variability was generally greater on the RBM platform than other assays, the more striking difference in the results from different assays was in magnitude. Where differences were observed between assays for an individual biomarker, they were seen in both sexes and consistent across samples collected at different time points. Differences of up to 15-fold were observed for some biomarker values between assays indicating that results generated using different assays should not be compared. For 8 biomarkers, there was compelling evidence for a sex difference. Baseline values in males were significantly higher than in females for total protein, β2-microglobulin, clusterin, cystatin-C, glutathione-S-transferase (GST-α), tissue inhibitor of metalloproteinases (TIMP-1), and vascular endothelial growth factor (VEGF); female values were significantly higher than that of males for albumin. The largest sex differences (male greater than female by 2- to 11-fold) were seen with β2-microglobulin, GST-α, and TIMP-1. These data add substantially to the limited body of knowledge in this area and provide a useful framework for evaluation of the potential relevance of sex differences in the diagnostic performance of these biomarkers.

Liver Microvascular Injury and Thrombocytopenia of Antibody-Calicheamicin Conjugates in Cynomolgus Monkeys - Mechanism and Monitoring

Purpose: Adverse reactions reported in patients treated with antibody–calicheamicin conjugates such as gemtuzumab ozogamicin (Mylotarg) and inotuzumab ozogamicin include thrombocytopenia and sinusoidal obstruction syndrome (SOS). The objective of this experimental work was to investigate the mechanism for thrombocytopenia, characterize the liver injury, and identify potential safety biomarkers. Experimental Design: Cynomolgus monkeys were dosed intravenously at 6 mg/m2/dose once every 3 weeks with a nonbinding antibody–calicheamicin conjugate (PF-0259) containing the same linker-payload as gemtuzumab ozogamicin and inotuzumab ozogamicin. Monkeys were necropsied 48 hours after the first administration (day 3) or 3 weeks after the third administration (day 63). Results: PF-0259 induced acute thrombocytopenia (up to 86% platelet reduction) with nadirs on days 3 to 4. There was no indication of effects on megakaryocytes in bone marrow or activation of platelets in peripheral blood. Microscopic evaluation of liver from animals necropsied on day 3 demonstrated midzonal degeneration and loss of sinusoidal endothelial cells (SECs) associated with marked platelet accumulation in sinusoids. Liver histopathology on day 63 showed variable endothelial recovery and progression to a combination of sinusoidal capillarization and sinusoidal dilation/hepatocellular atrophy, consistent with early SOS. Among biomarkers evaluated, there were early and sustained increases in serum hyaluronic acid (HA) that correlated well with serum aspartate aminotransferase and liver microscopic changes, suggesting that HA may be a sensitive diagnostic marker of the liver microvascular injury. Conclusions: These data support the conclusion that target-independent damage to liver SECs may be responsible for acute thrombocytopenia (through platelet sequestration in liver sinusoids) and development of SOS. Clin Cancer Res; 23(7); 1760–70. ©2016 AACR.

Comparison between male and female Sprague-Dawley rats in the response of urinary biomarkers to injury induced by gentamicin.

Differences were examined between male and female Sprague-Dawley rats in the response of 16 urinary biomarkers (measured using several assay platforms) to renal injury produced by gentamicin administered subcutaneously for 10 days at a dosage of 75 mg/kg. Urinary biomarkers expressed as fold difference from contemporaneous controls and renal histopathology were assessed after 3 and 10 doses. On day 4, minimal proximal tubular changes were observed microscopically in all males but no females; on day 11, more extensive and more severe injury was observed to a similar extent in all animals of both sexes. Modest increases (maximum 5-fold) in all urinary biomarkers (except epidermal growth factor [EGF], which was decreased) on day 4 and marked elevations (maximum 271-fold) on day 11 were seen consistently in both sexes. However, the magnitude of the increases differed between the sexes. On day 4, despite the lack of tubular injury, many biomarkers were more elevated in females than males but this rarely led to statistically significant sex differences; only 2 biomarkers (β2-microglobulin and total protein) showed a greater increase in males than females in line with the histopathology. On day 11, there were many more biomarkers that showed a statistically significant difference between the sexes in fold change with treatment; in line with the results on day 4, the majority of biomarkers were more increased in females than males. It remains unresolved if sex differences in the magnitude of biomarker response at injury threshold would lead to any difference in diagnostic interpretation between the sexes. These data highlight the need for publication of more studies using animals of both sexes to fully explore the influence of sex on the diagnostic performance of the novel biomarkers.

Improving the Safety Profile of ADCs

Antibody–drug conjugates (ADCs) take advantage of the specificity of a monoclonal antibody to deliver cytotoxic agents directly into tumor cells. The plethora of ADCs investigated in clinical trials in recent years has enabled characterization of the major challenges faced by this therapeutic modality. With regard to safety, non-target-mediated toxicities, which are independent of the targeted antigens and similar for ADCs with the same linker-payloads, often drive dose-limiting events in patients and at the same time question the targeting efficiency of current ADCs. Development-limiting target-mediated toxicities have only been reported for a few ADCs. This manuscript will provide an overview of the major clinically relevant toxicities of ADCs with a presentation of key ADC attributes influencing these toxicities and discussion of potential mechanisms. Current research efforts to mitigate ADC-associated toxicities, including among others site-specific conjugation chemistry and prevention of normal tissue binding, will be presented and could be critical to future ADC endeavors.

Abstract LB-202: Liver microvascular injury and thrombocytopenia of antibody-calicheamicin conjugates: mechanism and monitoring

Gemtuzumab ozogamicin (Mylotarg, GO) and inotuzumab ozogamicin (IO) are antibody-drug conjugates (ADCs) comprised of different humanized monoclonal antibodies (against CD33 and CD22 antigen, respectively) and of the same acid-labile linker and calicheamicin payload. GO and IO are developed for the treatment of acute myeloid leukemia and acute lymphoblastic leukemia, respectively. Adverse events reported with these 2 drugs in patients include thrombocytopenia and liver toxicity, which is characterized by increases in serum aminotransferases and bilirubin along with occasional cases of sinusoidal obstruction syndrome (SOS). The platelet and liver effects were seen in patients with conjugates targeting unrelated antigens and are likely target-independent. Since the specific mechanisms of these toxicities remain elusive, an investigative study was performed in cynomolgus monkeys with a non-binding ADC containing the same linker and payload as GO and IO, PF-0259, with the objectives to investigate the mechanism for thrombocytopenia, characterize the liver injury and identify potential safety biomarkers. Cynomolgus monkeys were dosed intravenously with PF-0259 at 6 mg/m 2 /dose once every 3 weeks for up to 3 doses and were necropsied 48 hours after the 1 st administration (Day 3) or 3 weeks after the 3 rd administration (Day 63). PF-0259 induced acute thrombocytopenia (up to 86% reduction in platelet count) in monkeys with nadirs on Days 3-4. There was no indication of effects on megakaryocytes in bone marrow or activation of platelets in peripheral blood. Microscopic evaluation of liver samples from animals necropsied on Day 3 demonstrated midzonal degeneration and loss of sinusoidal endothelial cells (SECs) associated with marked platelet accumulation in sinusoids. Liver histopathology on Day 63 showed variable endothelial cell recovery and progression to a combination of sinusoidal capillarization and sinusoidal dilation/hepatocellular atrophy, consistent with early SOS. Among biomarkers evaluated, there were early and sustained increases in serum hyaluronic acid (HA) that correlated well with AST levels and liver microscopic changes, suggesting that HA could be a sensitive diagnostic marker of the liver microvascular injury. In conclusion, this work has demonstrated that target-independent damage to liver SECs was responsible for acute thrombocytopenia (through platelet sequestration in the liver) and development of early SOS in monkeys. The translation of these observations to humans has not been evaluated. We further hypothesize that this toxicity mechanism may operate for other types of non-calicheamicin based ADCs in patients where adverse events of thrombocytopenia, increased liver enzymes and liver microvascular disorders (including nodular regenerative hyperplasia) have been observed. Citation Format: Magali Guffroy, Hadi Falahatpisheh, Kathleen Biddle, John Kreeger, Leslie Obert, Karen Walters, Richard Goldstein, Germaine Boucher, Timothy Coskran, William Reagan, Danielle Sullivan, Sharon Sokolowski, Richard Giovanelli, Hans-Peter Gerber, Martin Finkelstein, Nasir Khan. Liver microvascular injury and thrombocytopenia of antibody-calicheamicin conjugates: mechanism and monitoring. [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 LB-202.

Abstract 1220: A novel PTK7-targeted antibody-drug conjugate eliminates tumor-initiating cells and induces sustained tumor regressions

Disease relapse after treatment is common in triple-negative breast cancer (TNBC), ovarian cancer and non-small cell lung cancer (NSCLC). Therapies that target tumor-initiating cells (TICs) should improve patient survival by eliminating the cells that can drive tumor regrowth and metastasis. Here we identify Protein Tyrosine Kinase 7 (PTK7), a highly conserved but catalytically inactive receptor tyrosine kinase, as an antigen that is enriched on TICs in low-passage patient-derived xenografts (PDX) of TNBC, NSCLC and other tumor types. An anti-PTK7 antibody-drug conjugate (ADC) was generated from a humanized anti-PTK7 monoclonal antibody, a cleavable valine-citrulline-based linker and the Aur0101 auristatin microtubule inhibitor. The anti-PTK7 ADC induced sustained regressions of TNBC, NSCLC and ovarian cancer PDX, with improved activity over standard-of-care chemotherapy, and reduced the frequency of TICs as determined by serial transplantation experiments. Moreover, the ADC may have additional mechanisms of action, including an anti-angiogenic effect, that promote anti-tumor immune responses. Together these preclinical results indicate the potential of the anti-PTK7 ADC to improve the long-term survival of cancer patients. The ADC is currently being tested in a Phase 1 clinical trial, from which interim results will be presented. Citation Format: Marc Isaac Damelin, Alex Bankovich, Jeff Bernstein, Justin Lucas, Liang Chen, Sam Williams, Albert Park, Jorge Aguilar, Elana Ernstoff, Manoj Charati, Russell Dushin, Amy Jackson-Fisher, Monette Aujay, Christina Lee, Hanna Ramoth, Milly Milton, Johannes Hampl, Sasha Lazetic, Virginia Pulito, Douglas Armellino, Edward Rosfjord, Magali Guffroy, Hadi Falahatpisheh, Lindsay King, Frank Barletta, Robert Stull, Marybeth Pysz, Paul Escarpe, David Liu, Orit Foord, Brenda Gibson, Eric Powell, Christopher O’Donnell, Xiaohua Xin, Hans Peter Gerber, Puja Sapra, Scott Dylla. A novel PTK7-targeted antibody-drug conjugate eliminates tumor-initiating cells and induces sustained tumor regressions. [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 1220.

Abstract 2669: Targeting the tumor vasculature with antibody drug conjugates

Clinical use of vascular targeting antibody drug conjugates (VT-ADCs) has not yet been explored. Herein, we preclinically demonstrate utility, mechanisms and advantages of VT-ADCs as targeted cancer therapeutics. A monoclonal human IgG 1 antibody selective for murine VEGFR2 (B3) is non-VEGF-A neutralizing and traffics to the lysosome. B3 was conjugated to a proprietary auristatin microtubule inhibitor with a non-cleavable maleimidocaproyl linker, resulting in the proof-of-concept VT-ADC, B3-mcMTI. In vitro, free-payload and anti-VEGFR2-mcMTI selectively inhibit proliferating endothelial cells (ECs) with pM and low nM IC 50 s - suggesting that even with a broadly expressed, low-level target, a VT-ADC should be potent and tumor specific. To test this in vivo, we treated three cell line xenografts (CLX, HT29, Ls174T, A498) and a colorectal carcinoma patient derived xenograft (CRC PDX) with B3-mcMTI at 3 mg/kg q4d, resulting in tumor stasis in four models. In the HT29 colon carcinoma CLX and the CRC PDX model, B3-mcMTI was superior to VEGF-neutralizing antibody G6-31 (anti-VEGF mAb). In standard-of-care (SOC) chemotherapy (irinotecan and 5-FU) combination studies in HT29, B3-mcMTI had improved anti-tumor activity over SOC alone, and, moreover, was as effective in inhibiting tumor growth as a single agent ADC as anti-VEGF mAb combined with SOC. In the 4T1 orthotopic anti-VEGF resistant breast carcinoma setting, B3-mcMTI outperformed anti-VEGF mAb, and when combined with SOC (paclitaxel) demonstrated improved activity over single agent without an increase in metastases. B3-mcMTI internalization in endothelial cells is VEGFR2-mediated, with antibody binding and active payload releasing in normal and tumor tissues at concentrations above the in vitro IC 50 s; however, payload activity as measured by quantitative image analysis of pharmacodynamic biomarkers such as phospho-Histone H3 and cleaved caspase 3 is overwhelmingly localized to tumor ECs. Targeted vessels are smooth muscle invested, suggesting that VT-ADCs may target vasculature that contributes to anti-VEGF resistance. In conclusion, VT-ADCs are effective both as single agents and when combined with SOC, and VT-ADCs may overcome resistance mechanisms to standard anti-angiogenics. Taken together, these data suggest that payloads selective for proliferating ECs enable ADC-mediated targeting of widely expressed EC surface proteins, supporting the clinical pursuit of VT-ADCs. Citation Format: Andrea T. Hooper, Chao-Pei Betty Chang, Kimberly Marquette, Jonathon Golas, Justin Lucas, Timothy Nichols, Judy Lucas, Gavriil Maria, Edward Rosfjord, Anton Xavier, Nathan Scott, Sadhana Jain, Wei Cao, Mauricio Leal, Andreas Maderna, Magali Guffroy, Xiang Zheng, Lioudmila Tchistiakova, Frank Loganzo, Hans-Peter Gerber, Chad May. Targeting the tumor vasculature with antibody drug conjugates. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2669. doi:10.1158/1538-7445.AM2014-2669