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Background: Sacituzumab govitecan (SG) is an antibody-drug conjugate targeting Trop2 with an SN-38 payload recently approved for pretreated patients with locally advanced or metastatic triple-negative breast cancer (TNBC). The XenoSTART Patient-Derived Xenograft (XPDX) breast cancer platform includes over 180 models spanning all subtypes characterized with immunohistochemistry (IHC) including ER, PR, and HER2 protein levels, genomic and transcriptomic sequencing, and in vivo drug sensitivity. To better understand potential benefit of SG in breast cancers other than TNBC and further annotate our platform, Trop2 protein levels were determined in all breast models by IHC. We evaluated tumor growth inhibition by SG in 125 of our XPDX breast models and compared protein expression with agent activity. Methods: 180 breast XPDX models were evaluated for Trop2 expression (AF650, R&D Systems) and 125 were evaluated in vivo against SG; responses were grouped by ER and Trop2 status (+/-). Models were grown subcutaneously in female athymic nude mice and ER+ models supplemented with estradiol. Models were also characterized for PR, HER2, and AR protein expression by IHC and profiled using WES and RNAseq. For in vivo studies, SG was administered by intravenous injection biweekly for two cycles at 1 mg, flat; endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C< 0%) versus Day 0 tumor volume was also reported. Results: 180 breast models were examined by IHC with 75/180 (42%) classified as ER+ and 105/180 (58%) ER-. In ER+ models 38/75 (51%) were Trop2+ and 37/75 (49%) Trop2-, and in ER- models 41/105 (39%) were Trop2+ and 64/105 (61%) Trop2-. In vivo, 20% of ER+/Trop2+ models reported sensitivity to SG, most notably models from patients with acquired resistance to CDK4/6 inhibitors, including STM001 and ST4316B. Interestingly, >70% of ER+/HER2+/Trop2+ models were insensitive to SG, including ST225 and ST340. Of 41 ER-/Trop2+ models, approximately 40% reported some response to SG with 50% of these sensitive to therapy, including ST5954 established from a patient who began treatment with SG following sample collection and is currently in remission. >75% of Trop2- models were insensitive to SG regardless of ER status. Conclusion: We screened 180 models in our XPDX breast cancer platform for Trop2 expression and compared expression with in vivo SG efficacy in 125 models. Analysis is underway to correlate receptor and molecular profiles with SG sensitivity in breast models and we are expanding expression and in vivo testing to additional indications. Citation Format: Alyssa Simonson, Johnnie Flores, Ebony Anderson, Crystal Moreno, George Plasko, Kyriakos P. Papadopoulos, Amita Patnaik, Drew Rasco, Gladys Rodriguez, Amy Lang, Muralidhar Beeram, Luis Rodriguez, Ronald Drengler, Steven Abbate, Hanni Salih, Lon Smith, Maryam Elmi, Brittany DeBerry, Arthur Rosenthal, Tatiana Hernandez, Nehal Lakhani, Manish Sharma, Michael Wick. Correlation of Trop2 expression with in vivo sensitivity to sacituzumab govitecan in a panel of breast XPDX models [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-08-05.

Supplementary Tables S1-2, Figure 1. Supplementary Table S1. Matrix view of Part A-2 dose titration and PK sampling scheme. Supplementary Table S2. Efficacy outcomes by investigator review per RECIST v1.1. Supplementary Figure 1. Seventeen patients were tested with IFN-γ ELISPOT assay.

Figure S1. Seventeen patients were tested with IFN-γ ELISPOT assay.

Purpose: This phase I study evaluated the safety, maximum tolerated dose, antitumor activity, and pharmacokinetics and pharmacodynamics of pembrolizumab in patients with advanced solid tumors.Experimental Design: In a 3 + 3 dose escalation study, 10 patients received pembrolizumab 1, 3, or 10 mg/kg intravenously every 2 weeks until progression or intolerable toxicity. Seven additional patients received 10 mg/kg every 2 weeks. Thirteen patients participated in a 3-week intrapatient dose escalation (dose range, 0.005–10 mg/kg) followed by 2 or 10 mg/kg every 3 weeks. Tumor response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.Results: No dose-limiting toxicities were observed. Maximum administered dose was 10 mg/kg every 2 weeks. One patient with melanoma and one with Merkel cell carcinoma experienced complete responses of 57 and 56+ weeks' duration, respectively. Three patients with melanoma experienced partial responses. Fifteen patients with various malignancies experienced stable disease. One patient died of cryptococcal infection 92 days after pembrolizumab discontinuation, following prolonged corticosteroid use for grade 2 gastritis considered drug related. Pembrolizumab exhibited pharmacokinetic characteristics typical of humanized monoclonal antibodies. Maximum serum target engagement was reached with trough levels of doses greater than or equal to 1 mg/kg every 3 weeks. Mechanism-based translational models with a focus on intratumor exposure prediction suggested robust clinical activity would be observed at doses ≥2 mg/kg every 3 weeks.Conclusions: Pembrolizumab was well tolerated and associated with durable antitumor activity in multiple solid tumors. The lowest dose with full potential for antitumor activity was 2 mg/kg every 3 weeks. Clin Cancer Res; 21(19); 4286–93. ©2015 AACR.See related commentary by van Elsas et al., p. 4251

Background: First-line treatment for some cancer types includes platinum-based therapy. While the rate of initial response to treatment is high, most patients develop platinum-resistant disease. Current salvage therapy provides benefit to some patients, demonstrating the need for additional effective therapies. To assist in identifying new therapies, we have established XenoSTART patient-derived xenograft (XPDX) models representing breast, ovary, uterine, and lung cancers. Each model was characterized by DNA/RNA analysis, sensitivity to platinum treatment, and annotated with donor patient treatment status at the time of sample collection. Methods: 210 XPDX models were evaluated in this screen including 66 breast, 56 ovary, 36 uterine, and 52 lung xenografts. WES and RNAseq were performed on each model and patient treatment history and outcome annotated. For in vivo studies, models were implanted into female nudes and administered (IP; q7dx3) 3 m/k cisplatin or 60 m/k carboplatin. Study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Results: Study results are summarized below in Table 1: Sequencing identified several variants in resistant, chemo-naïve models including point mutations in RAS/RAF/MET/PIK3CA genes and others, while sensitive models lacked common driver mutations. Conclusion: We have characterized 210 XPDX models. Uterine models were most often resistant to platinum, while almost 1/2 of ovary and 1/3 of breast models were sensitive, regardless of treatment status. Only 15% of lung models were sensitive to platinum; cancer driver variants were found in several models. Overall, we report differential platinum sensitivity in a panel of diverse models useful in understanding mechanisms of resistance and for development of effective therapies in platinum-resistant cancers. Table 1. Type Breast Ovary Uterine Lung Total 66 56 36 52 # Sensitive 25 25 9 8 % 38% 45% 25% 15% Naïve 11 16 8 5 % 44% 64% 89% 63% P-1st 6 6 1 2 % 24% 24% 11% 25% P-2nd+ 6 3 0 1 % 24% 12% 0% 13% # Insensitive 41 31 27 44 % 62% 55% 75% 85% Naïve 11 9 20 21 % 27% 29% 74% 48% P-1st 14 10 5 13 % 34% 32% 19% 30% P-2nd+ 16 12 2 10 % 39% 39% 7% 23% Naïve=No Prior Treatment; P-1st=Post 1st Line Therapy; P-2nd=Post 2nd+ Line Therapy Citation Format: Alyssa Simonson, Johnnie Flores, Lizette Firova, Christian Hernandez, Morgan Harris, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Allan White, Lon Smith, Ronald Drengler, Amy Lang, Murali Beeram, Michael J. Wick. Correlation of platinum sensitivity with donor patient treatment status in a panel of breast, ovary, uterine, and lung XPDX 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 1092.

Background: Neuregulin-1 (NRG1) rearrangements drive cancers by binding to ERBB3/ERBB2 heterodimers and activating downstream signaling. NRG1 fusion proteins have recently been identified in several cancer types including lung and ovary. To better understand the role of NRG1 fusions in cancer we established three XenoSTART patient-derived xenograft (XPDX) models driven by NRG1 rearrangements including two CD74-NRG1 lung models designated ST2891 and ST3204 and one SARAF-NRG1 ovary model designated ST2476. These models were established in athymic nude mice and characterized for receptor expression, genomic alterations, and in vivo drug sensitivity. Methods: ST2891 was established from an excision biopsy collected from a 68-year-old male with NSCLC following treatment with carboplatin/paclitaxel and carboplatin/pemetrexed. ST3204 was established from a lymph node biopsy collected from a 63-year-old female with NSCLC following treatment with cisplatin/pemetrexed. ST2476 was established from primary tissue collected from a chemo naïve 61-year-old female with ovarian cancer. The resulting models were passaged and characterized using immunohistochemical and genomic analysis including WES and RNAseq. In vivo studies were performed testing various chemotherapy and targeted agents; study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C Results: All models reported ERBB2 and ERBB3 staining in evaluated passages with similar histology compared with archival clinical samples. WES analysis of the three models did not identify any variants in EGFR/ERBB2-4/RAS/RAF genes. RNA sequencing revealed CD74-NRG1 or SARAF-NRG1 gene fusions independently confirmed using molecular studies. In vivo, both lung models were resistant to weekly cisplatin or T-DM1 and daily palbociclib (50 mg/kg) or daily afatinib up to 10 mg/kg. ST3204 was found sensitive to weekly pertuzumab (1 mg/kg). Both lung models were resistant to trastuzumab (1 mg/kg). The ST2476 ovary XPDX was found resistant to endocrine therapies and reported some sensitivity to weekly cisplatin. Conclusion: We have established and characterized a panel of three XPDX models driven by NRG1 rearrangements including two CD74-NRG1 lung models and one SARAF-NRG1 ovary model. These models are valuable tools for further developing therapies targeting NRG1-driven cancers. Citation Format: Alyssa Simonson, Johnnie Flores, Crystal Moreno, Justine Hruzek, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Ronald Drengler, Allan White, Jun Ma, Michael J. Wick. Establishment and characterization of neuregulin-1 (NRG1) fusion driven XPDX 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 353.

Background: We previously reported (RAS AACR 2022) a preclinical screen testing KRASG12C-inhibitors (KRASG12C-i) in 13 colorectal and 13 lung KRASG12C XPDX models; all tested models were from patients naïve to KRASG12C-i. To better understand mechanisms of resistance in this agent class, we established three lung XPDX models designated ST5185B, ST5431B, and ST5489 from patients before therapy with a KRASG12C-i. We also established one colorectal XPDX, designated ST4859, post therapy. Once established these models were molecularly characterized, in vivo sensitivity to sotorasib and adagrasib determined, and results compared with clinical response. Ex vivo cultures and 3D-XPDX࣪ studies were also performed evaluating both compounds comparing drug sensitivity. Methods: Lung: ST5185B was established from a pretreated 68-year-old male; ST5431B was established from a chemo-naïve 67-year-old male; additional samples were collected during and after progression on KRASG12C-i and are currently in development. ST5489 was established from a pretreated 64-year-old female. CRC: ST4859 was established from a 57-year-old female pretreated with a KRASG12C-i; all patients received at least one cycle of KRASG12C-i therapy. Models were WES and RNA sequenced and sotorasib and adagrasib sensitivity determined. For each study, agents were dosed PO once daily at 100 mg/kg; study endpoints included tumor volume and time from treatment initiation with %T/C values reported at study completion; a %T/C of ≤ 20% was considered sensitive. Results: In all models sequencing confirmed KRASG12C and other variants previously identified with clinical studies. In vivo studies identified ST5185B as resistant to sotorasib (%T/C=70%) and adagrasib (%T/C=86%); this donor patient progressed after six weeks on KRASG12C-i therapy. ST5431B reported sensitivity to both therapies; this donor patient had a partial response (50% decrease) for six months prior to progression. ST5489 reported sensitivity to sotorasib (%T/C=14%) and adagrasib (%T/C=8%); this donor patient interrupted dosing due to KRASG12C-i intolerance and discontinued therapy, with disease progression after five weeks. ST4859 reported resistance to both drugs; this donor patient had stable disease on KRASG12C-i therapy for approximately seven months prior to progression. Ex vivo cultures and 3D-XPDX࣪ studies from all models reported sensitivity to both agents similar to in vivo studies. Summary: We developed, evaluated, and correlated in vivo sensitivity of sotorasib and adagrasib in a panel of four XPDX models established from patients receiving KRASG12C-i therapy. Studies are underway to generate drug-resistant clones of sensitive models and to elucidate mechanisms of drug resistance in ST4859. Citation Format: Johnnie Flores, Alyssa Simonson, Peter Forofontov, Anna Stackpole, Drew Rasco, Amita Patnaik, Kyriakos Papadopoulos, Teresa DesRochers, Natalie Williams, Ronald Drengler, Lon Smith, Michael J. Wick. Correlation of drug sensitivity to clinical response in XPDX models established from patients treated with KRAS-G12C-inhibitor therapy [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 412.

Background: 15-20% of metastatic breast cancers are characterized by overexpression or amplification of human epidermal growth factor receptor 2 (HER2). First-line treatment for HER2-positive metastatic breast cancer includes the anti-HER2 monoclonal antibodies trastuzumab and pertuzumab in combination with chemotherapy. Second-line therapy includes T-DM1, an antibody-drug conjugate (ADC) consisting of trastuzumab conjugated to maytansinoid (DM1). Until recently, patients who progress on T-DM1 were left with few treatment options. Trastuzumab deruxtecan (DS-8201a) is an antibody-drug conjugate (ADC) consisting of an anti-HER2 (human epidermal growth factor receptor 2) antibody linked to a novel topoisomerase I inhibitor payload using a cleavable tetrapeptide-based linker and was recently approved for unresectable or T-DM1-refractory HER2+ breast cancer. In addition, DS-8201a is currently being evaluated as a treatment in breast cancers with low and medium expression of HER2. To better understand the potential for DS-8201a as a treatment in these cancer types, we evaluated this therapy in a panel of ER+/- XPDX models with differential HER2 expression. In addition, we compared DS-8201a activity to T-DM1 and benchmarked efficacy of the topoisomerase I inhibitor irinotecan in all tested models. Methods: One hundred (50ER+/50ER-) breast XPDX models were evaluated in this study. Models were established and characterized for estrogen receptor and HER2 expression by IHC and profiled using WES and RNAseq. For in vivo studies, DS-8201a and T-DM1 were administered IV at 3 mg/kg and irinotecan IP at 100 mg/kg on a weeklyx3 schedule. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Results: Models were grouped by ER positivity (+/-) and model HER2 score and designated as null (0), low (1+), medium (2+) or high (3+); models established from clinically HER2+ patients were also noted. In the ER+ group, HER2 low and medium expressing models accounted for over 80% of the total, while 15% were categorized as high and less than 5% as null. All models with high and 30% with medium HER2 staining were from clinically HER2+ patients, no low or null models were established from breast cancer assigned HER2+ clinically. In the ER- group, HER2 low and medium expressing models accounted for 75% of the total, while 12% were categorized as high and 13% as null. All models with high and 13% with medium HER2 staining were from clinically HER2+ patients; 5% of low or null models were established from breast cancer assigned HER2+ clinically. In vivo, 65% of the ER+ group reported sensitivity to DS-8201a versus 25% to T-DM1; 10% of DS-8201a, and 40% of T-DM1 sensitive models were high expression models and the remaining low and medium with no null models reporting sensitivity to either agent. 35% of tested ER+ models were sensitive to both HER2 therapies and 50% of models sensitive to DS-8201a were also sensitive to irinotecan. In the ER- group, 70% reported sensitivity to DS-8201a versus 25% to T-DM1; 20% of DS-8201a and 25% of T-DM1 sensitive models were high expression models and the remaining low and medium with one null model (ST069) sensitive to both agents. 25% of tested ER- models were sensitive to both HER2 therapies and 40% of models sensitive to DS-8201a were also sensitive to irinotecan. Conclusion: We have compared activity of DS-8201a, T-DM1 and irinotecan in a panel of ER+/- XPDX models and correlated activity based on HER2 expression. This data and panel can be utilized as a valuable tool in better understanding the potential for DS-8201a and other HER2-targeting therapies as a treatment in cancers driven by HER2 expression. Citation Format: Alyssa Simonson, Peter Forofontov, Johnnie R Flores, Kimberly Hernandez, April Cabang, Amy Lang, Gladys Rodriguez, Kyriakos Papadopoulos, Murali Beeram, Arthur Rosenthal, Brittany DeBerry, Lon Smith, Ronald Drengler, Amita Patnaik, Drew Rasco, Luis Rodriguez, Steven Abbate, Scott Ulmer, Michael Wick. Correlation of HER2 receptor expression and in vivo activity of the HER2-targeting therapies trastuzumab deruxtecan (DS-8201a) and T-DM1 activity in a panel of breast XPDX models [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-01-04.

Background: Fulvestrant is a selective estrogen receptor modulator (SERM) approved as a single agent for estrogen receptor positive, HER2 negative breast cancer patients at various stages of disease and in combination with CDK4/6 inhibitors following endocrine therapy failure. Although this agent requires intramuscular injection, it has demonstrated superior activity and fewer side effects versus some oral endocrine treatments however, resistance to fulvestrant often develops. To better understand fulvestrant resistance and its utility in patients who have failed other endocrine therapies, we evaluated the agent in a panel of ER+ breast models established from patients at various stages of disease representing endocrine-sensitive and -resistant disease. Methods: Sixty-five previously developed ER+ breast XPDX models were evaluated in this study. Models were grown subcutaneously in female athymic nude mice supplemented with estradiol in drinking water when necessary. All models were characterized at early and late passages for estrogen receptor expression by immunohistochemistry and profiled using WES and RNAseq. For in vivo studies, fulvestrant was administered by subcutaneous injection at 2.5 or 5 mg per dose once weekly until study completion. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C Citation Format: April Cabang, Crystal Moreno, Johnnie R Flores, Jenna Boedeker, Alyssa Simonson, Jun Ma, Amy Lang, Gladys Rodriguez, Arthur Rosenthal, Kyriakos Papadopoulos, Amita Patnaik, Drew Rasco, Lon Smith, Murali Beeram, Ronald Drengler, Luis Rodriguez, Steven Abbate, Scott Ulmer, Michael J Wick. Nonclinical activity of fulvestrant in a panel of ER+ breast XPDX models representing clinically acquired and innate resistance to endocrine therapies [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-01-11.

Purpose: This phase I study evaluated the safety, maximum tolerated dose, antitumor activity, and pharmacokinetics and pharmacodynamics of pembrolizumab in patients with advanced solid tumors. Experimental Design: In a 3 + 3 dose escalation study, 10 patients received pembrolizumab 1, 3, or 10 mg/kg intravenously every 2 weeks until progression or intolerable toxicity. Seven additional patients received 10 mg/kg every 2 weeks. Thirteen patients participated in a 3-week intrapatient dose escalation (dose range, 0.005–10 mg/kg) followed by 2 or 10 mg/kg every 3 weeks. Tumor response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Results: No dose-limiting toxicities were observed. Maximum administered dose was 10 mg/kg every 2 weeks. One patient with melanoma and one with Merkel cell carcinoma experienced complete responses of 57 and 56+ weeks' duration, respectively. Three patients with melanoma experienced partial responses. Fifteen patients with various malignancies experienced stable disease. One patient died of cryptococcal infection 92 days after pembrolizumab discontinuation, following prolonged corticosteroid use for grade 2 gastritis considered drug related. Pembrolizumab exhibited pharmacokinetic characteristics typical of humanized monoclonal antibodies. Maximum serum target engagement was reached with trough levels of doses greater than or equal to 1 mg/kg every 3 weeks. Mechanism-based translational models with a focus on intratumor exposure prediction suggested robust clinical activity would be observed at doses ≥2 mg/kg every 3 weeks. Conclusions: Pembrolizumab was well tolerated and associated with durable antitumor activity in multiple solid tumors. The lowest dose with full potential for antitumor activity was 2 mg/kg every 3 weeks. Clin Cancer Res; 21(19); 4286–93. ©2015 AACR. See related commentary by van Elsas et al., p. 4251

Background: Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate (ADC) approved for treatment of HER2 positive (HER2+), trastuzumab-resistant breast cancers. While this agent is initially effective, resistance often develops. To aid in developing new therapies for HER2+, T-DM1-resistant breast cancer and better understanding resistance mechanisms, we established PDX models designated ST340, ST1339, and ST2167 from three patients with trastuzumab-resistant HER2+ breast cancer and sensitive to T-DM1 treatment in vivo. A cohort of each model was conditioned in vivo with chronic T-DM1 treatment to generate drug resistance. These models, designated ST340/TDR, ST1339/TDR, and ST2167/TDR were subjected to characterization and efficacy studies, and the results compared with parent models. Methods: ST340, ST1339, and ST2167 were established from patients who responded then progressed on trastuzumab and other therapies. The models were passaged, and cohorts were challenged with chronic T-DM1 treatment to produce drug resistance. The parent and resistant models were subjected to various comparative analyses including receptor expression, RNAseq, and response to various relevant therapies. Results: T-DM1-resistant models retained high HER2 expression and demonstrated receptor staining and histopathology comparable to respective parent lines. Comparison of parent and resistant clones using RNAseq identified several alterations in variants and expression. In vivo T-DM1 reported significant activity towards ST340: %T/C=3%, ST1339: %T/C=-40% and ST2167: %T/C=13% versus control, including tumor regressions in ST1339. T-DM1-resistant models reported the following values following treatment: ST340/TDR: %T/C=65%, ST1339/TDR: %T/C=58% and ST2167/TDR: T/C=91%. Conclusion: We have established and characterized three paired T-DM1-sensitive and resistant breast PDX models, which can be utilized as valuable tools in developing new therapies for T-DM1-resistant patients. Citation Format: Alyssa Moriarty, Lizette Gamez, Tomoyuki Mashimo, Kyriakos Papadopoulos, Amita Patnaik, Drew Rasco, Amy Lang, Ronald Drengler, Michael J Wick. Development and characterization of HER2+ T-DM1-resistant breast PDX models in athymic nude mice [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A017. doi:10.1158/1535-7163.TARG-19-A017

Background: FDA-approved CDK 4/6 inhibitors (CDK4/6i) including palbociclib, abemaciclib, and ribociclib have demonstrated clinical benefit in treating hormone receptor-positive (HR+) breast cancer. However, whether there is differential sensitivity to each therapy in vivo is unknown. In addition, whether these inhibitors demonstrate activity towards other tumor types is unclear. To better understand potential differences in CDK4/6i activity, we compared activity of each in a panel of 100 HR+/- breast cancer PDX models. To identify additional tumor types sensitive to CDK4/6i, we screened single agent palbociclib in an additional panel of 350 PDX models representing solid and hematologic malignancies. FFPE samples were collected from control and treatment groups in all studies at endpoint, and %T/C values in each model were calculated and in breast studies compared. Methods: START PDX models were established and validated as previously described and further characterized using IHC, WES, RNAseq, and drug sensitivity studies. For each CDK4/6i study, models were implanted SC in immune-deficient mice and studies initiated at 200-300 mm3 (n=1-3/grp). CDK4/6i agents were administered orally once daily at 50-75 mg/kg for a minimum of twenty-eight days or until study completion. Models tested with palbociclib included breast, lung, ovary, pancreas, head/neck, renal, gastric, uterine, colorectal, melanoma, and various hematologic malignancies. Study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20% versus control was considered sensitive. Partial tumor regression (PR) (%PR=1-99%) and complete tumor regression (CR) (%CR=100%) values versus Day 0 tumor volume of treated groups were also reported. Results: HR+/- breast models demonstrated variable sensitivity to the three CDK4/6i with HR+ models established from chemo-naïve patients reporting greatest tumor growth inhibition (TGI). Two of four HR+ ESR1 mutant models reported modest sensitivity to CDK4/6i (ST941Y537S and ST2535D538G), while ST2177Y537S was sensitive and ST2056Y537S refractory to the three therapies. Evaluation of palbociclib in additional indications reported notable TGI versus control in several indications with the following percentage of tested models reporting sensitivity: Lung: 10%, Ovary: 15%, Pancreas: 30%, Head/Neck: 35%, Renal: 45%, Gastric: 60%, Uterine: 20%, Colorectal: 45%, Melanoma: 40% and Hematologic: 15%. In addition, several indications reported tumor regressions including one CR (lung: ST1748) and partial responses in ovary, pancreas, head/neck, renal, colorectal, and melanoma. Conclusion: We evaluated and compared three FDA-approved CDK4/6i therapies in a panel of HR+/- breast PDX models and identified models with differential responses. In addition, we screened single agent palbociclib in a panel of 350 PDX models representing solid and hematologic malignancies and identified several sensitive models in multiple indications, including some with partial or complete tumor regressions. Citation Format: Lizette Gamez, Tomoyuki Mashimo, Alyssa Moriarty, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Amy Lang, Ronald Drengler, Lon Smith, Michael J Wick. PDX-based screen to evaluate and compare approved CDK4/6 inhibitors in breast cancer and determine palbociclib efficacy in additional tumor types [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A008. doi:10.1158/1535-7163.TARG-19-A008

Preclinical in vivo models of estrogen receptor positive (ER+) breast cancer rely on exogenous supplementation of hormones for growth. This requirement leads to animal toxicity and mortality over time, limiting development and drug testing in these types of models. Efficacy of test agents, particularly endocrine therapies, may also be altered in these models due to excessive hormone exposure, highlighting the need to improve methods for the establishment and testing of ER+ breast models. We have developed an alternative method of hormone supplementation in ER+ breast cancer models and optimized this method for testing of endocrine therapies. Using two cell-based breast models, we demonstrated improved breast tumor take and time to tumor volume endpoint while reducing animal toxicity and mortality associated with standard hormone supplementation. Subsequent studies identified the lowest effective dose (LED) of supplement for hormone dependent model growth with a preclinically relevant time to tumor volume endpoint. Activity of endocrine therapies including tamoxifen, letrozole, fulvestrant and exemestane were compared at the standard and LED hormone concentrations. In these studies tamoxifen treatment resulted in tumor regressions which was not appreciably improved using the LED dose of supplement. However letrozole activity was improved in the LED study suggesting hormone supplementation can impact activity of some agents. Using this process we also generated a panel of ER+ patient-derived xenograft (PDX) models, including two novel hormone therapy responsive models from chemo-naïve or hormone therapy pretreated patients, designated ST986 and ST2177, respectively. This improved method of hormone supplementation diminishes the adverse effects of standard hormone supplementation and provides utility for development of anticancer therapies in ER+ breast models. Citation Format: Wick MJ, Vaught T, Meade J, Gamez L, Farley M, Tolcher AW, Rasco D, Patnaik A, Drengler RL, Rosenthal A, Papadopoulos KP. Establishment and evaluation of ER+ breast cancer models using an optimized methodology for exogenous hormone delivery. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-03-05.

Based on the preclinical evidence of topoisomerase I (Topo-1) upregulation by mitomycin C(MMC) and decreased NF-kappaB activation by celecoxib, we evaluated combinations of irinotecan/MMC and irinotecan/MMC/celecoxib in patients with advanced solid malignancies.Initially, patients received MMC on day 1 and irinotecan on days 2, 8, 15 and 22, every 6 weeks. MMC dose was fixed at 6 mg/m(2) and cumulative doses of36 mg/m(2) were not permitted. Irinotecan was escalated in 25 mg/m(2) increments. Due to late-onset diarrhea, the schedule was subsequently shortened to 4 weeks, omitting irinotecan on days 15 and 22. In the second part of the study, celecoxib 400 mg orally twice daily was added to irinotecan/MMC regimen. Potential pharmacokinetic interactions and Topo-1 and DT-diaphorase (NQ01) gene expressions in peripheral-mononuclear cells were evaluated.Forty-five patients were enrolled. Irinotecan 125 mg/m(2) on days 2 and 8 in combination with MMC 6 mg/m(2) on day 1 every 4 weeks is recommended for future studies; myelosuppression and diarrhea are dose-limiting. The addition of celecoxib resulted in unacceptable toxicities despite reductions on irinotecan's dose. No relevant pharmacokinetic interactions occurred between irinotecan and MMC, and mean increases in Topo-1, were observed. Sixteen of 36 patients evaluable for response-assessment had discernable anti-tumor activity, including 1 complete, 4 partial, 10 minor and 1 tumor marker response. Four patients had prolonged (4 months) disease-stability (stable disease, not included in CR or PR). Patients experiencing complete and partial responses had higher increments in Topo-1 expression.Modulation of irinotecan by MMC is feasible, devoid of pharmacological interactions and active in solid malignancies. The lack of improvement in therapeutic index does not support the addition of celecoxib.

PURPOSE: To evaluate the toxicity and pharmacologic behavior of the novel mushroom-derived cytotoxin irofulven administered as a 5-minute intravenous (IV) infusion daily for 5 days every 4 weeks to patients with advanced solid malignancies. PATIENTS AND METHODS: In this phase I trial, 46 patients were treated with irofulven doses ranging from 1.0 to 17.69 mg/m2 as a 5-minute IV infusion (two patients received a 1-hour infusion) daily for 5 days every 4 weeks. The modified continual reassessment method was used for dose escalation. Pharmacokinetic studies were performed on days 1 and 5 to characterize the plasma disposition of irofulven. RESULTS: Forty-six patients were treated with 92 courses of irofulven. The dose-limiting toxicities on this schedule were myelosuppression and renal dysfunction. At the 14.15-mg/m2 dose level, renal dysfunction resembling renal tubular acidosis occurred in four of 10 patients and was ameliorated by prophylactic IV hydration. The 17.69-mg/m2 dose level was not tolerated because of grade 4 neutropenia and renal toxicity, whereas the 14.15-mg/m2 dose level was not tolerable with repetitive dosing because of persistent thrombocytopenia. Other common toxicities included mild to moderate nausea, vomiting, facial erythema, and fatigue. One partial response occurred in a patient with advanced, refractory metastatic pancreatic cancer lasting 7 months. Pharmacokinetic studies of irofulven revealed dose-proportional increases in both maximum plasma concentrations and area under the concentration-time curve, while the agent exhibited a rapid elimination half-life of 2 to 10 minutes. CONCLUSION: Given the results of this study, the recommended dose of irofulven is 10.64 mg/m2 as a 5-minute IV infusion daily for 5 days every 4 weeks. The preliminary antitumor activity documented in a patient with advanced pancreatic cancer and the striking preclinical antitumor effects of irofulven observed on intermittent dosing schedules support further disease-directed evaluations of this agent on the schedule evaluated in this study.

Summary Background: This study was performed to evaluate the pharmacokinetics, bioequivalence, and feasibility of a combined oral formulation of 5-flurouracil (5-FU) and eniluracil (Glaxo Wellcome Inc., Research Triangle Park, North Carolina), an inactivator of dihydropyrimidine dehydrogenase (DPD). The rationale for developing a combined eniluracil/5-FU formulation oral dosing form is to simplify treatment with these agents, which has been performed using separate dosing forms, and decrease the probability of severe toxicity and/or suboptimal therapeutic results caused by inadvertently high or conversely insufficient 5-FU dosing. Patients and methods: The trial was a randomized, threeway crossover bioequivalence study of three oral dosing forms of eniluracil/5-FU tablets in adults with solid malignancies. Each period consisted of two days of treatment and a five- to seven-day washout phase. Eniluracil at a dose of 20 mg, which results in maximal DPD inactivation, was administered twice daily on the first day and in the evening on the second day of each of the three treatments. On the morning of the second day, all patients received a total eniluracil dose of 20 mg orally and a total 5-FU dose of 2 mg orally as either separate tablets (treatment A) or combined eniluracil/5-FU tablets in two different strengths (2 tablets of eniluracil/5-FU at a strength (mg/mg) of 10/1 (treatment B) or 8 tablets at a strength of 2.5/0.25 (treatment Q). The pharmacokinetics of plasma 5-FU, eniluracil, and uracil, and the urinary excretion of eniluracil, 5-FU, uracil, and a-fluoro-(3-alanine (FBAL), were studied. To determine the bioequivalence of the combined eniluracil/5-FU dosing forms compared to the separate tablets, an analysis of variance on pharmacokinetic parameters reflecting eniluracil and 5-FU exposure was performed. Results: Thirty-nine patients with advanced solid malignancies had complete pharmacokinetic studies performed during treatments A, B, and C. The pharmacokinetics of eniluracil and 5-FU were similar among the three types of treatment. Both strengths of the combined eniluracil/5-FU dosing form and the separate dosing forms were bioequivalent. Mean values for terminal half-life, systemic clearance, and apparent volume of distribution for oral 5-FU during treatments A/B/C were 5.5/5.6/5.6 hours, 6.6/6.6/6.5 liters/hour, and 5O.7/51.5/5O.0 liters, respectively. The intersubject coefficient of variation for pharmacokinetic variables reflecting 5-FU exposure and clearance in treatments ranged from 23% to 33%. The urinary excretion of unchanged 5-FU over 24 hours following treatments A, B, and C averaged 52.2%, 56.1%, and 50.8% of the administered dose of 5-FU, respectively. Parameters reflecting DPD inhibition, including plasma uracil and urinary FBAL excretion following treatments A, B, and C were similar. Toxicity was generally mild and similar following all three types of treatments. Conclusions: The pharmacokinetics of 5-FU and eniluracil were similar and met bioequivalence criteria following treatment with the separate oral formulations of 5-FU and eniluracil and two strengths of the combined formulation. The availability of a combined eniluracil/5-FU oral dosing form will likely simplify dosing and decrease the probability of severe toxicity or suboptimal therapeutic results caused by an inadvertent 5-FU overdose or insufficient 5-FU dosing in the case of separate oral formulations, thereby enhancing the overall feasibility and therapeutic index of oral 5-FU therapy.

PURPOSE: To evaluate the maximum-tolerated dose, dose-limiting toxicities (DLTs), and pharmacokinetic profile of vesnarinone given once daily in combination with gemcitabine. PATIENTS AND METHODS: Twenty-six patients were treated with oral vesnarinone once daily on a continuous schedule at doses of 60, 90, 120, 150, and 180 mg in combination with intravenous (IV) gemcitabine at a dose of 1,000 mg/m2 on days 1, 8, and 15 every 4 weeks. To determine whether biologically relevant concentrations were being achieved, predose concentrations (Cmin) of vesnarinone were obtained weekly. Plasma gemcitabine and 2′,2′-difluorodeoxyuridine concentrations were obtained during courses 1 and 2. RESULTS: Twenty-six patients were treated with 92 courses of vesnarinone/gemcitabine. The principal toxicities of the regimen consisted of neutropenia and thrombocytopenia, which were dose-limiting in two of eight heavily pretreated new patients treated at the 90 mg/1,000 mg/m2 dose level and one of 10 minimally pretreated new patients at the 120 mg/1,000 mg/m2 dose level. None of three patients treated with 15 courses at the vesnarinone/gemcitabine dose levels of 60 mg/1,000 mg/m2 experienced DLT. Pharmacokinetic studies of vesnarinone revealed significant interpatient variability at any given dose level. There was evidence of a linear relationship between vesnarinone dose and mean Cmin at dosages of vesnarinone less than 150 mg, with plateauing of mean Cmin values at higher dosages. There was no impact of vesnarinone on gemcitabine concentrations, and the vesnarinone pharmacokinetics did not change with gemcitabine between weeks 1 and 2. Two partial responses occurred in patients with refractory breast and non–small-cell lung carcinoma. CONCLUSION: When combined with gemcitabine, the recommended dose of vesnarinone for phase II evaluations is 90 mg orally once daily with gemcitabine 1,000 mg/m2 IV on days 1, 8, and 15 every 4 weeks. There is no evidence of pharmacokinetic interaction between vesnarinone and gemcitabine. Further studies of vesnarinone as a single agent or in combination with gemcitabine and other antineoplastic agents are warranted.

PURPOSE: To assess the feasibility of administering DX-8951f (exatecan mesylate), a water-soluble, camptothecin analog, as a 30-minute intravenous infusion daily for 5 days every 3 weeks, determine the maximum-tolerated dose (MTD) and pharmacokinetic (PK) behavior of DX-8951f, and seek preliminary evidence of anticancer activity. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with escalating doses of DX-8951f. After three patients were treated at the first dose level, doses were to be escalated in increments of 100%, using a single patient at each dose level unless moderate toxicity was observed. The MTD, defined as the highest dose level at which the incidence of dose-limiting toxicity did not exceed 20%, was calculated separately for minimally pretreated (MP) and heavily pretreated (HP) patients. The PK and excretory profiles of DX-8951, the anhydrous form of DX-8951f, were also characterized. RESULTS: Thirty-six patients were treated with 130 courses of DX-8951f at six dose levels ranging from 0.1 to 0.6 mg/m2/d. Brief, noncumulative neutropenia was the most common toxicity observed. Severe myelosuppression (neutropenia that was protracted and/or associated with fever and/or severe thrombocytopenia) was consistently experienced by HP and MP patients at doses exceeding 0.3 and 0.5 mg/m2/d, respectively. Nonhematologic toxicities (nausea, vomiting, and diarrhea) were also observed, but these effects were rarely severe. Objective antitumor activity included partial responses in one patient each with platinum-resistant extrapulmonary small-cell and fluoropyrimidine- and irinotecan-resistant colorectal carcinoma, and minor responses in patients with prostate, hepatocellular, thymic, primary peritoneal, and irinotecan-resistant colorectal carcinomas. The PKs of total DX-8951 were linear and well fit by a three-compartment model. CONCLUSION: The recommended doses for phase II studies of DX-8951f as a 30-minute infusion daily for 5 days every 3 weeks are 0.5 and 0.3 mg/m2/d for MP and HP patients, respectively. The characteristics of the myelosuppressive effects of DX-8951f, paucity of severe nonhematologic toxicities, and antitumor activity against a wide range of malignancies warrant broad disease-directed evaluations of DX-8951f on this schedule.

PURPOSE: To evaluate the clinical feasibility and pharmacologic behavior of the platelet-derived growth factor (PDGF) tyrosine kinase inhibitor SU101, administered on a prolonged, intermittent dosing schedule to patients with advanced solid malignancies. PATIENTS AND METHODS: Twenty-six patients were treated with SU101 doses ranging from 15 to 443 mg/m2 as a 24-hour continuous intravenous (IV) infusion weekly for 4 weeks, repeated every 6 weeks. Pharmacokinetic studies were performed to characterize the disposition of SU101 and its major active metabolite, SU0020. Immunohistochemical staining of PDGF-α and -β receptors was performed on malignant tumor specimens obtained at diagnosis. RESULTS: Twenty-six patients were treated with 52 courses (187 infusions) of SU101. The most common toxicities were mild to moderate nausea, vomiting, and fever. Two patients experienced one episode each of grade 3 neutropenia at the 333 and 443 mg/m2 dose levels. Dose escalation of SU101 above 443 mg/m2/wk was precluded by the total volume of infusate required, 2.5 to 3.0 L. Individual plasma SU101 and SU0020 concentrations were described by a one-compartment model that incorporates both first-order formation and elimination of SU0020. SU101 was rapidly converted to SU0020, which exhibited a long elimination half-life averaging 19 ± 12 days. At the 443 mg/m2/wk dose level, trough plasma SU0020 concentrations during weeks 2 and 4 ranged from 54 to 522 μmol/L. Immunohistochemical studies revealed PDGF-α and -β receptor staining in the majority (15 of 19) of malignant neoplasms. CONCLUSION: SU101 was well tolerated as a 24-hour continuous IV infusion at doses of up to 443 mg/m2/wk for 4 consecutive weeks every 6 weeks. Although further dose escalation was precluded by infusate volume constraints, this SU101 dose schedule resulted in the achievement and maintenance of substantial plasma concentrations of the major metabolite, SU0020, for the entire treatment period.

PURPOSE To evaluate the feasibility of administering biricodar (VX-710; Incel, Vertex Pharmaceuticals Inc, Cambridge, MA), an agent that modulates multidrug resistance (MDR) conferred by overexpression of both the multidrug resistance gene product (MDR1) P-glycoprotein and the MDR-associated protein (MRP) in vitro, in combination with paclitaxel. The study also sought to determine the maximum-tolerated dose (MTD) of paclitaxel that could be administered with biologically relevant concentrations of VX-710 and characterize the toxicologic and pharmacologic profiles of the VX-710/ paclitaxel regimen. PATIENTS AND METHODS Patients with solid malignancies were initially treated with VX-710 as a 24-hour infusion at doses that ranged from 10 to 120 mg/m2 per hour. After a 2-day washout period, patients were re-treated with VX-710 on an identical dose schedule followed 8 hours later by paclitaxel as a 3-hour infusion at doses that ranged from 20 to 80 mg/m2. The pharmacokinetics of both VX-710 and paclitaxel were studied during treatment with VX-710 alone and VX-710 and paclitaxel. Thereafter, patients received VX-710 and paclitaxel every 3 weeks. RESULTS VX-710 alone produced minimal toxicity. The toxicologic profile of the VX-710/paclitaxel regimen was similar to that reported with paclitaxel alone; neutropenia that was noncumulative was the principal dose-limiting toxicity (DLT). The MTD levels of VX-710/ paclitaxel were 120 mg/m2 per hour and 60 mg/m2, respectively, in heavily pretreated patients and 120/60 to 80 mg/m2 per hour in less heavily pretreated patients. At these dose levels, VX-710 steady-state plasma concentrations (Css) ranged from 2.68 to 4.89 microg/mL, which exceeded optimal VX-710 concentrations required for MDR reversal in vitro. The pharmacokinetics of VX-710 were dose independent and not influenced by paclitaxel. In contrast, VX-710 reduced paclitaxel clearance. At the two highest dose levels, which consisted of VX-710 120 mg/m2 per hour and paclitaxel 60 and 80 mg/m2, pertinent pharacokinetic determinants of paclitaxel effect were similar to those achieved with paclitaxel as a 3-hour infusion at doses of 135 and 175 mg/m2, respectively. CONCLUSION VX-710 alone is associated with minimal toxicity. In combination with paclitaxel, biologically relevant VX-710 plasma concentrations are achieved and sustained for 24 hours, which simulates optimal pharmacologic conditions required for MDR reversal in vitro. The acceptable toxicity profile of the VX-710/ paclitaxel combination and the demonstration that optimal pharmacologic conditions for MDR reversal are achievable support a rationale for further trials of VX710/paclitaxel in patients with malignancies that are associated with de novo or acquired resistance to paclitaxel caused by overexpression of MDR1 and/or MRP.

Background: Recent FDA approval of B-Raf and Mek inhibitors has improved treatment outcomes for patients with BRAFV600E/K metastatic melanoma. However, most patients receiving these agents progress within a year and are left with limited treatment options. Few validated screening tools exist to evaluate potentially beneficial therapies for these resistant/refractory patients. To address this deficiency we have established patient-derived xenograft (PDX) model sets by collecting serial samples at timepoints when patients demonstrated sensitivity and resistance to B-Raf and Mek inhibitors and characterized each by mutation, receptor and ligand density and drug sensitivity. Methods: Paired, sensitive/insensitive PDX melanoma models from three patients were established in athymic nude mice from primary or metastatic patient tissue. Baseline samples for each paired model were collected from patients who subsequently reported clinical response to a therapy and again once the patient progressed on that therapy. Established models were confirmed by histologic comparative analysis and linked with patient treatment and outcome data. For each model DNA was extracted and subjected to exon sequencing of 207 known oncogenes; growth factor receptor and ligand densities were interrogated using immunohistochemistry and quantitative RNA in situ hybridization. Drug sensitivity studies were performed evaluating and comparing each model following treatment with oral vemurafenib, trametinib or dabrafenib. Study endpoints included tumor volume and time from treatment initiation, with tumor growth inhibition, delay and regression reported at study completion. Results: The B-RafV600E models ST052, ST052B, ST052C and ST052D reported sensitivity or resistance to vemurafenib correlative with clinical response and progression. Trametinib but not vemurafenib was active towards the ST361 B-RafV600R model while the ST361B model was found insensitive to both agents. Trametinib sensitivity to the ST697 and ST697B H-RasQ61K models was correlative with clinical response and progression. Dabrafenib sensitivity was similar to vemurafenib in evaluated models. Expression of HER3, a mechanism of possible adaptive resistance to targeted therapies, but not EGFR or HER2 was reported in all models and was relatively unchanged in serial models sets; heregulin expression was also determined in each model. Conclusion: We have established patient-derived xenograft (PDX) model sets with sensitivity and resistance to B-Raf and Mek inhibitors correlative with clinical response and progression. Receptor and ligand expression was identified and maintained in serial models. Based on these results this panel can serve as a valuable screening tool to evaluate potentially beneficial therapies for patients resistant/refractory to B-Raf and Mek inhibitors. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C10. Citation Format: Michael J. Wick, Justin Meade, Jennifer Brown, Teresa L. Vaught, Anthony W. Tolcher, Lizette Gamez, Drew Rasco, Amita Patnaik, Ronald Drengler, Kyriakos P. Papadopoulos. Establishment and characterization of melanoma patient-derived xenograft (PDX) model sets: correlation with clinical response and progression using serial biopsy sampling. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C10.

Background: The START Patient Tumor Program was established to improve clinical outcomes for cancer patients by creating a biorepository of blood and cancer tissues for characterization and preclinical model development and testing. To date samples from over 1500 patients have been collected with over 400 models generated including 40 patient-derived breast tumor xenografts. These models can be used for personalized studies, particularly in situations where treatment options have been exhausted. In the current study a breast biopsy was collected from a 48 year old Hispanic female with recurrent, chemotherapy-refractory ER+/HER2+ metastatic breast cancer and implanted into an immune-deficient mouse. The resulting model was expanded and evaluated against eight FDA-approved and four investigational agents. Methods: ST340 ER+/HER2+ breast PDX model: The tumor sample from an inform-consented participant was implanted into nude mice and the established model confirmed by histologic analysis and linked with clinical treatment and outcome data. Activating mutation profiling was performed on fifty-two known cancer genes with extracted DNA using a PCR-based assay with customized primers. An efficacy study was performed testing various approved and investigational agents. Study endpoints included tumor volume and time from treatment initiation. Reported results included tumor growth inhibition or delay and regression. Results: Prior to treatment initiation, estradiol was withheld to confirm dependence and was found requisite for growth. Following treatment, results identified impressive sensitivity to the targeted therapy everolimus including tumor regressions and moderate sensitivity towards an aromatase inhibitor. Treatment with this combination regimen resulted in improved tumor markers and overall quality of life for an extended period of time. Following progression, subsequent treatment with a cytotoxic agent found active in the initial screen resulted in additional months of progression free disease. Conclusion: Participation in the START Patient Tumor Program provided beneficial data which improved clinical outcome for this patient demonstrating that personalized preclinical models of human cancer can predict useful agents for clinical treatment in select situations. Citation Format: Michael J. Wick, Teresa L. Vaught, Lizette Gamez, Jennifer Brown, Alyssa Moriarty, Anthony W. Tolcher, Drew W. Rasco, Amita Patnaik, Gladys Rodriguez, Ronald L. Drengler, Kyriakos P. Papadopoulos. Establishment and characterization of a clinically-relevant personalized hormone-dependent breast cancer tumor model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1398. doi:10.1158/1538-7445.AM2013-1398

Background: Vemurafenib is a recently approved anticancer therapy for B-RafV600E metastatic melanoma. Treatment with this agent increases overall patient survival compared with dacarbazine; however, most patients receiving vemurafenib progress within a year and are left with limited treatment options. Few validated screening tools exist to evaluate potentially beneficial therapies for these resistant/refractory patients. To address this deficiency we have generated a panel of paired mutant B-Raf vemurafenib-sensitive and -resistant patient-derived xenograft (PDX) models of metastatic melanoma and colorectal cancer. Each parent model was screened for activating mutations and all evaluated in vivo against vemurafenib. In addition, select model pairs were subjected to whole genome sequencing and RNA analysis to identify differences in genetic and expression profiles. Methods: Establishment of parent models was previously described. Vemurafenib-resistant PDX models (PDX-VR) were generated by in vivo administration of clinical-grade vemurafenib at increasing concentrations over limited tumor passages. Parental vemurafenib-sensitive models were screened for activating mutations of fifty-two known cancer genes using a PCR-based assay with customized primers. DNA and RNA was extracted from select model pairs and profiled and compared for alterations. Results: To date we have generated six B-RafV600E PDX-VR models (3 melanoma + 3 colorectal) with additional B-RafV600E and B-RafV600K PDX-VR models in development. In vivo studies evaluating vemurafenib in parent models reported notable tumor growth inhibition in all but one colorectal model (ST428), including tumor regressions in melanoma. PDX-VR models reported tumor growth similar to untreated controls at vemurafenib concentrations up to 150 mg/kg/day. Comparative analysis of paired models revealed some differences in DNA and RNA profiles. Conclusion: We have generated a panel of paired mutant B-raf vemurafenib-sensitive and -resistant patient-derived xenograft (PDX) models representing metastatic melanoma and colorectal cancer available as validated screening tools to evaluate potentially beneficial therapies for vemurafenib-resistant/refractory patients. Citation Format: Michael J. Wick, Teresa L. Vaught, Lizette Gamez, Justin Meade, Skylar Carden, Anthony W. Tolcher, Drew W. Rasco, Amita Patnaik, Alexander Miller, Ronald Drengler, Kyriakos P. Papadopoulos. Establishment and characterization of paired mutant B-raf, vemurafenib-sensitive and -resistant patient-derived xenograft models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2037. doi:10.1158/1538-7445.AM2013-2037

2512 Background: Programmed death-1 (PD-1) is an inhibitory T-cell coreceptor that may lead to suppression of antitumor immunity. MK-3475 is a humanized monoclonal IgG4 antibody against PD-1. Preclinically, MK-3475 has shown antitumor activity in multiple tumor types. This first-in-human phase I trial explored safety, PK, PD, and antitumor activity of MK-3475. Methods: An open-label, dose escalation study was conducted in patients with advanced malignancy refractory to standard therapy. Cohorts of 3-6 patients were enrolled (3+3 design) at escalating IV doses of 1, 3, and 10 mg/kg. Following an initial dose and 28-day Cycle 1, patients were allowed to subsequently receive multiple doses given every 2 wks. Radiographic assessment was conducted every 8 wks using RECIST 1.1 guidelines. Results: Nine patients, 3 at each dose level, completed the dose-limiting toxicity (DLT) period (28 d). Patients had non–small cell lung cancer (NSCLC, n=3), rectal cancer (n=2), melanoma (MEL, n=2), sarcoma (n=1), or carcinoid (n=1). To date, a total of 63 doses were administered (median 7/patient; max 12) without DLT. Drug-related adverse events (AEs) across all doses included Grade 1 fatigue (n=3), nausea (n=2), diarrhea (n=1), dysgeusia (n=1), breast pain (n=1), and pruritus (n=1). One drug-related Grade 2 AE of pruritus was reported. No drug-related AEs ≥ Grade 3 were observed. PK data are shown in the table. Based on RECIST, 1 patient with MEL on therapy >6 mths had a partial response, and preliminary evidence of tumor size reduction (stable disease) was observed in 3 additional patients with advanced cancer. Conclusions: MK-3475 was well-tolerated without DLT across 3 tested dose levels. Evidence of antitumor activity was observed. Enrollment continues to obtain additional safety, PK, and efficacy data; updated data will be presented at the meeting. [Table: see text]

2555 Background: Tesetaxel (TST) has anticancer activity in patients (pts) with metastatic breast cancer (MBC) and gastric cancer when administered orally once every 3 weeks (Q3W). This drug is not a Pgp substrate, does not cause hypersensitivity reactions, and may be associated with less neurotoxicity. The maximally tolerated dose (MTD) on the Q3W schedule is 27 mg/m2, and neutropenia is dose-limiting. Since taxane activity may be schedule-dependent, we conducted a weekly, dose-ranging, and PK evaluation of TST. Methods: Eligibility: advanced solid tumors; ECOG PS 0-2; adequate organ function. TST was given once weekly for 3 weeks in a 28-day cycle, beginning at a total flat dose of 25 mg/cycle with progressive increases in total dose up to 75 mg/cycle. Subsequently, dosing was converted to a weight-based regimen at weekly doses of 12.5, 15, and 17.5 mg/m2 (i.e., total per cycle dose up to 52.5 mg/m2). Serial plasma samples were assayed by HPLC. Results: 26 pts were treated in 8 dose cohorts. The MTD was 15 mg/m2/wk (total cycle dose, 45 mg/m2). With repeated cycles, constitutional symptoms (fatigue and anorexia) rather than neutropenia proved dose-limiting at 17.5 mg/m2/wk. Only 1 pt (at 12.5 mg/m2/wk) developed grade 3 neutropenia; no other episodes of Grade 3-4 myelotoxicity were observed. One pt with MBC (who had progressed after 2 prior taxane regimens) achieved a PR; 1 pt with prostate cancer has maintained prolonged reduction of PSA (> 57%). PK analyses showed low but progressive increases in trough TST concentrations (0.4–4.6 nmol/mL) 7 days after each succeeding dose, which was consistent with the prolonged T½ of this drug (~180 hrs). There was no substantial drug accumulation over multiple cycles. Conclusions: Weekly oral TST is safe, provides long-term low-level drug exposure, and increases the total delivered dose over 12 wks by 25%. Interestingly, this regimen is not associated with significant myelosuppression. Thus, weekly TST dosing provides a highly convenient, “dose-dense”, taxane regimen that is not associated with neutropenia, which should facilitate its integration into multiple chemotherapy regimens. An ongoing study is evaluating efficacy of weekly TST dosing in MBC.

Background: Patient-derived tumor models passaged only a few times in vivo retain physical and molecular characteristics of human cancer and may prove essential in identifying disease biomarkers and drug targets in later stage development. Currently we have collected tumor tissue from chemo-naïve and pretreated patients and established and characterized a panel of low passage colorectal tumor models. Methods: For each model, tissue was implanted into immune-deficient mice and once established, each model was confirmed by histologic analysis and linked with donor patient treatment and outcome data. Model characterization including mutation profiling and drug sensitivity studies were performed and results compared with clinical patient information; each model was evaluated with the EGFR inhibitor cetuximab and two standard clinical therapies FOLFOX and irinotecan and compared with patient's drug sensitivity before and after tissue sample collection. Single agent tumor growth inhibition was evaluated and study endpoints included mean control tumor volumes of approximately 1 cm3 or up to sixty days following treatment initiation. Results: Eighteen low passage colorectal models have been established and characterized. KRAS mutations were identified in 44% of models and activating mutations identified in some models include: PI3KCA (6%), TP53 (33%) and BRAF (6%). In vivo response to FOLFOX and irinotecan correlated to ≥65% of donor patient outcome to these treatments. Cetuximab sensitivity did not fully correlate with Ras mutation status as 4/6 wildtype and 4/8 Ras demonstrated cetuximab sensitivity in these studies. Conclusion: We have generated a panel of low passage colorectal tumor models with differential mutation status and drug sensitivity profiles. Expansion of this panel of patient-derived tumors is planned and should further enhance its utility in identifying agents potentially useful for treatment of colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B17.

Activating mutations of the BRAF gene occurs in approximately 60% of melanomas, most often resulting in a V600E mutant. Other substitutions at this and adjacent residues are known to exist, resulting in constitutive B-raf kinase activity and poor clinical prognosis. B-raf mutations may also play a role in the pathogenesis of a number of other malignancies including colorectal, lung, thyroid and hematopoietic cancers. Due to the importance of this target in cancer progression, several potential therapies targeting B-raf are currently in preclinical and clinical development. To better understand the role of B-raf in melanoma and other cancers we have established and characterized a panel of wildtype and mutated B-raf melanoma, colorectal, ovary and biliary cancer patient-derived tumor models. For each model, tissue was implanted into immune-deficient mice and once established, each model was confirmed by histologic analysis and linked with donor patient treatment and outcome data. In addition, model characterization including mutation profiling and drug sensitivity studies were performed and results compared with clinical information. Finally we evaluated relevant B-raf wildtype and mutant models with the B-raf inhibitor vemurafenib. Eighteen low passage melanoma models have been established, nine with confirmed mutated BRAF genes. Four additional mutant B-Raf tumor models include two colorectal one ovary and one biliary cancer. Model information and identified mutations are as follows: Additional gene mutations identified include KRAS (9%), NRAS (9%), TP53 (14%) and CTNNB1 (5%). Differential activity was reported for single agent temozolomide, carboplatin and paclitaxel in melanoma model studies. In the majority, there was no correlation between mutation status and cytotoxic drug sensitivity. However, two B-raf models with identical mutations demonstrated sensitivity to irinotecan with sustained partial tumor regressions. Additional drug screens of two multi-mutated models, ST004 and ST054, showed resistance to all evaluated therapies. The ST274 (BRAF-D594G) melanoma model was found insensitive to vemurafenib; results from other models are pending. Conclusion: We have generated and a panel of patient-derived tumor models which include B-raf wildtype and mutated melanoma, colorectal, ovary and biliary cancers possessing differential mutation status and drug sensitivity profiles. Expansion of this panel of tumors is planned and should further enhance its utility in development of useful agents towards melanoma and other B-raf mutant cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B125.

Background: Ovarian cancer is the leading cause of death from gynecologic malignancies in Western countries. Standard treatment for ovarian cancer consists of tumor debulking followed by platinum/taxane therapy. While the rate of initial response to treatment is high, the majority of patients develop recurrent, chemoresistant disease. Secondary chemotherapy treatment provides benefit to only 10–30% of these patients, demonstrating the need for identifying additional useful therapies. To assist in identifying new therapies for ovarian cancer, we collected tumor tissue from chemo-naïve and pretreated patients and established, developed and characterized a panel of low passage ovarian tumor models. We then utilized these models to demonstrate antitumor activity of a novel targeted therapy. Methods: For each model, tissue was collected and implanted into immune-deficient mice and progress monitored. Each established model was confirmed by histologic comparison to the corresponding patient clinical sample and linked to their available treatment and outcome data. Additional characterization, including mutation profiling and standard drug sensitivity studies, was performed on each model and results compared with clinical information. An investigator-initiated study was performed evaluating activity of the Smac (second mitochondrial-derived activator of caspases) mimetic TL32711 in a subset of these models. Single agent tumor growth inhibition and delay were evaluated and study endpoints included mean and individual tumor volumes of approximately 1 cm3 or up to sixty days following treatment initiation. Results: Twenty low passage ovarian models have been established and characterized. Activating mutations identified in some models include: PI3KCA (6%), TP53 (19%), FBXW7 (6%), RAS (13%) and BRAF (6%). In vivo response to platinum and/or taxane agents correlated ≥70% with donor patient outcome at the time of sample collection and models demonstrated variable sensitivity to evaluated secondary chemotherapies. Single agent TL32711 showed statistically significant (p Conclusion: We have generated a panel of characterized patient-derived low passage ovarian tumor models with differential mutation status and drug sensitivity profiles. Using these models we have identified a preclinically active agent towards ovarian cancer. Expansion of this panel of ovarian tumors is planned and should further enhance its utility in identifying agents potentially useful for treatment of ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B13.

501 Background: Pharmacogenomic studies have documented the importance of CYP2D6 in the metabolism of tamoxifen (TAM) and the resulting clinical outcomes. However, there is no data relating polymor...

Patients (pts) with pancreatic cancer have very poor survival. A substantial percentage of pancreatic cancers have increased expression of SPARC (Secreted Protein And Rich in Cysteine) (Guweidhi et al., Annals of Surgery, 2005; 242: 224-234,Von Hoff et al., J Clin Oncol 2006; 24(18s): 138, Infante et al., J Clin Oncol 2007; 25 (3): 319.) Increased SPARC expression has been correlated with improved response to nanoparticle albumin-bound paclitaxel(nab-paclitaxel) due to a SPARC-albumin interaction (Trieu et al., New Targets in Delivery System for Diagnosis and Treatment (SKCC), 2007; abstract 53). Based on this observation, SPARC may play a role in selectively concentrating nab-paclitaxel in pancreatic tumors. Therefore a disease specific modified phase I trial of nab-paclitaxel + gemcitabine in pts with advanced pancreatic cancer was performed. Tumor samples were obtained for SPARC evaluation and CA19-9 levels were monitored as a drop in CA19-9 has been correlated with improved survival. In this study, pts with advanced pancreatic cancer with no prior chemotherapy except as a radiation sensitizer received nab-paclitaxel + gemcitabine on days 1, 8, 15 every 28 days with a starting dose of 100 mg/m2 and 1000 mg/m2 respectively. Subsequent dose escalations of nab-paclitaxel were planned at 125 and 150mg/m2. To date, 20 pts have been recruited for this study. All of the pts received nab-paclitaxel 100mg/m2 + gemcitabine 1000 mg/m2. 18/20 patients completed at least one cycle of treatment and were considered evaluable. Independent review of the patient’s measurable disease on CAT and PET scans is ongoing with many of the patients continuing to have radiographic regression of disease. 17/18 evaluable subjects had paired CA19-9 levels available for analysis. Clinical activity has been demonstrated by CA19-9 reduction of greater than 20% from baseline in 82% (14/17pts) and more than 70% from baseline in 59% (10/17 pts). A decrease of CA19-9 of at least 20% has been associated with improvement in patient survival (AH Ko et al., BJC 2005; 93, 195-199, Park BB et al., Cancer Chemother Pharmacol 2007 Sep; 60 (4): 489-94, and Boeck S et al., Oncology 2006; 70 (4): 255-64). The most common Grade 3/4 adverse event (AE) was neutropenia (n=3, 2, respectively). Other grade 3 AEs include febrile neutropenia (1), fatigue (1) and hyperglycemia (1). In addition, 2 cases of grade 2 anemia and 2 cases of thrombocytopenia were observed. Based on these results, the combination of nab-paclitaxel and gemcitabine in pancreatic cancer warrants further study. Dose escalation to cohort 2 is proceeding. When the MTD is determined, that cohort will be expanded. The optimum dose as determined in this study will be used in a larger, randomized phase II/III study.

PURPOSE: To assess the feasibility of administering PN401, an oral uridine prodrug, as a rescue agent for the toxic effects of fluorouracil (5-FU), and to determine the maximum-tolerated dose of 5-FU when given with PN401, with an 8-hour treatment interval between these agents. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with escalating doses of 5-FU, given as a rapid intravenous infusion weekly for 3 consecutive weeks every 4 weeks. PN401 was administered orally 8 hours after 5-FU administration, to achieve sustained plasma uridine concentrations of at least 50 μmol/L. Initially, patients received 6 g of PN401 orally every 8 hours for eight doses (schedule 1). When dose-limiting toxicity (DLT) was consistently noted, patients then received 6 g of PN401 every 2 hours for three doses and every 6 hours thereafter for 15 doses (schedule 2). RESULTS: Twenty-three patients received 50 courses of 5-FU and PN401. Among patients on schedule 1, DLT (grade 4 neutropenia complicated by fever and diarrhea) occurred in those receiving 5-FU 1,250 mg/m2/wk. Among patients on schedule 2, 5-FU 1,250 mg/m2/wk was well tolerated, but grade 4, protracted (> 5 days) neutropenia was consistently noted in those treated with higher doses of the drugs. Nonhematologic effects were uncommon and rarely severe. The pharmacokinetics of 5-FU, assessed in 12 patients on schedule 2, were nonlinear, with the mean area under the time-versus-concentration curve (AUC) increasing from 298 ± 44 to 962 ± 23 μmol/L and mean clearance decreasing from 34 ± 4 to 15.6 ± 0.38 L/h/m2 as the dose of 5-FU was increased from 1,250 to 1,950 mg/m2/wk. 5-FU AUCs achieved with 5-FU 1,250 mg/m2/wk for 6 weeks along with the intensified PN401 dose schedule were approximately five-fold higher than those achieved with 5-FU alone. Plasma uridine concentrations increased with each of the three PN401 doses given every 2 hours, and uridine steady-state concentrations were greater than 50 μmol/L. CONCLUSION: Treatment with oral PN401 beginning 8 hours after 5-FU administration is well tolerated and results in sustained plasma uridine concentrations above therapeutic-relevant levels. The recommended 5-FU dosage for phase II evaluations is 1,250 mg/m2/wk for 3 weeks every 4 weeks with the intensified PN401 dose schedule (schedule 2). At this dose, systemic exposure to 5-FU as measured by AUC was five-fold higher than that observed after administration of a conventional 5-FU bolus.

PURPOSE: We conducted a phase I dose-escalation trial of orally administered irinotecan (CPT-11) to characterize the maximum-tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetic profile, and antitumor effects in patients with refractory malignancies. PATIENTS AND METHODS: CPT-11 solution for intravenous (IV) use was mixed with CranGrape juice (Ocean Spray, Lakeville-Middleboro, MA) and administered orally once per day for 5 days every 3 weeks to 28 patients. Starting dosages ranged from 20 to 100 mg/m2/d. RESULTS: Grade 4 delayed diarrhea was the DLT at the 80 mg/m2/d dosage in patients younger than 65 years of age and at the 66 mg/m2/d dosage in patients 65 or older. The other most clinically significant toxicity of oral CPT-11 was neutropenia. A linear relationship was found between dose, peak plasma concentration, and area under the concentration-time curve (AUC) for both CPT-11 and SN-38 lactone, implying no saturation in the conversion of irinotecan to SN-38. The mean metabolic ratio ([AUCSN-38 total + AUCSN-38G total]/AUCCPT-11 total) was 0.7 to 0.8, which suggests that oral dosing results in presystemic conversion of CPT-11 to SN-38. An average of 72% of SN-38 was maintained in the lactone form during the first 24 hours after drug administration. One patient with previously treated colorectal cancer and liver metastases who received oral CPT-11 at the 80 mg/m2/d dosage achieved a confirmed partial response. CONCLUSION: The MTD and recommended phase II dosage for oral CPT-11 is 66 mg/m2/d in patients younger than 65 years of age and 50 mg/m2/d in patients 65 or older, administered daily for 5 days every 3 weeks. The DLT of diarrhea is similar to that observed with IV administration of CPT-11. The biologic activity and favorable pharmacokinetic characteristics make oral administration of CPT-11 an attractive option for further clinical development.