A phase 1 study of veliparib (ABT-888) plus weekly carboplatin and paclitaxel in advanced solid malignancies, with an expansion cohort in triple negative breast cancer (TNBC) (ETCTN 8620)

BACKGROUND

Veliparib is a poly-ADP-ribose polymerase (PARP) inhibitor, and it has clinical activity with every 3 weeks carboplatin and paclitaxel. In breast cancer, weekly paclitaxel is associated with improved overall survival. We aimed to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of veliparib with weekly carboplatin and paclitaxel as well as safety, pharmacokinetics, and preliminary clinical activity in triple negative breast cancer (TNBC).

METHODS

Patients with locally advanced/metastatic solid tumors and adequate organ function were eligible. A standard 3 + 3 dose-escalation design was followed by a TNBC expansion cohort. Veliparib doses ranging from 50 to 200 mg orally bid were tested with carboplatin (AUC 2) and paclitaxel (80 mg/m2) given weekly in a 21-day cycle. Adverse events (AE) were evaluated by CTCAE v4.0, and objective response rate (ORR) was determined by RECIST 1.1.

RESULTS

Thirty patients were enrolled, of whom 22 had TNBC. Two dose-limiting toxicities were observed. The RP2D was determined to be 150 mg PO bid veliparib with weekly carboplatin and paclitaxel 2 weeks on, 1 week off, based on hematologic toxicity requiring dose reduction in the first 5 cycles of treatment. The most common grade 3/4 AEs included neutropenia, anemia, and thrombocytopenia. PK parameters of veliparib were comparable to single-agent veliparib. In 23 patients with evaluable disease, the ORR was 65%. In 19 patients with TNBC with evaluable disease, the ORR was 63%.

CONCLUSION

Veliparib can be safely combined with weekly paclitaxel and carboplatin, and this triplet combination has promising clinical activity.

Dose-dependent bioavailability, absorption-rate limited elimination, and tissue distribution of the ATR inhibitor BAY-1895344 (elimusertib) in mice

PURPOSE

Ataxia Telangiectasia and Rad3-related (ATR) is a pivotal component of the DNA damage response and repair pathways that is activated in responses to cytotoxic cancer treatments. Several ATR inhibitors (ATRi) are in development that block the ATR mediated DNA repair and enhance the damage associated with cytotoxic therapy. BAY-1895344 (elimusertib) is an orally available ATRi with preclinical efficacy that is in clinical development. Little is known about the pharmacokinetics (PK) which is of interest, because tissue exposure and ATR inhibition may relate to toxicities or responses.

METHODS

To evaluate BAY-1895344 PK, a sensitive LC-MS/MS method was utilized for quantitation in mouse plasma and tissues. PK studies in mice were first conducted to determine dose linearity. In vivo metabolites were identified and analyzed semi-quantitatively. A compartmental PK model was developed to describe PK behavior. An extensive PK study was then conducted in tumor-bearing mice to quantitate tissue distribution for relevant tissues.

RESULTS

Dose linearity was observed from 1 to 10 mg/kg PO, while at 40 mg/kg PO bioavailability increased approximately fourfold due to saturation of first-pass metabolism, as suggested by metabolite analyses and a developed compartmental model. Longer half-lives in PO treated mice compared to IV treated mice indicated absorption-rate limited elimination. Tissue distribution varied but showed extensive distribution to bone marrow, brain, and spinal cord.

CONCLUSIONS

Complex PK behavior was limited to absorption processes which may not be recapitulated clinically. Tissue partition coefficients may be used to contrast ATR inhibitors with respect to their efficacy and toxicity.

A phase 1 and pharmacodynamic study of chronically-dosed, single-agent veliparib (ABT-888) in patients with BRCA1- or BRCA2-mutated cancer or platinum-refractory ovarian or triple-negative breast cancer

PURPOSE

BRCA1 or BRCA2 mutated cancers (BRCAmut) have intrinsic sensitivity to PARP inhibitors due to deficiency in homologous recombination-mediated DNA repair. There are similarities between BRCAmut and BRCAwt ovarian and basal-like breast cancers. This phase I study determined the recommended phase II dose (RP2D) and preliminary efficacy of the PARP inhibitor, veliparib (ABT-888), in these patients.

PATIENTS AND METHODS

Patients (n = 98) were dosed with veliparib 50-500 mg twice daily (BID). The BRCAmut cohort (n = 70) contained predominantly ovarian (53%) and breast (23%) cancers; the BRCAwt cohort (n = 28) consisted primarily of breast cancer (86%). The MTD, DLT, adverse events, PK, PD, and clinical response were assessed.

RESULTS

DLTs were grade 3 nausea/vomiting at 400 mg BID in a BRCAmut carrier, grade 2 seizure at 400 mg BID in a patient with BRCAwt cancer, and grade 2 seizure at 500 mg BID in a BRCAmut carrier. Common toxicities included nausea (65%), fatigue (45%), and lymphopenia (38%). Grade 3/4 toxicities were rare (highest lymphopenia at 15%). Overall response rate (ORR) was 23% (95% CI 13-35%) in BRCAmut overall, and 37% (95% CI 21-55%) at 400 mg BID and above. In BRCAwt, ORR was 8% (95% CI 1-26%), and clinical benefit rate was 16% (95% CI 4-36%), reflecting prolonged stable disease in some patients. PK was linear with dose and was correlated with response and nausea.

CONCLUSIONS

Continuous veliparib is safe and tolerable. The RP2D was 400 mg BID. There is evidence of clinical activity of veliparib in patients with BRCAmut and BRCAwt cancers.

Dose-dependent bioavailability and tissue distribution of the ATR inhibitor AZD6738 (ceralasertib) in mice

PURPOSE

Ataxia telangiectasia and Rad3-related (ATR) initiates and regulates cellular responses to DNA damage, such as those caused by cancer treatments. Several ATR inhibitors (ATRi) are in clinical development including AZD6738. Therapeutic indices among ATRi may differ as a result of varying potencies and concentrations at both tumor and off-target sites. Additionally, AZD6738 contributes to anti-tumor immune responses necessitating evaluation of exposure at immunological sites.

METHODS

Using mouse models and a highly sensitive LC-MS/MS assay, the pharmacokinetics of AZD6738 were studied, including dose linearity, bioavailability, metabolism, and tissue distribution in tumor-bearing mice.

RESULTS

Initial studies identified dose-dependent bioavailability, with greater than proportional increases in exposure as dose increased resulting in a ~ twofold increase in bioavailability between the lowest and highest investigated doses. These behaviors were successfully captured with a compartmental PK model. Analysis of metabolite PK revealed decreasing metabolic ratios with increasing dose, indicative of saturable first-pass metabolism. Further analysis revealed that intestinal and gut metabolism contribute to metabolism and these saturable mechanisms. Studies of tumor and tissue distribution found rapid and extensive drug distribution to most tissues except brain and spinal cord.

CONCLUSION

The complex non-linear behavior of AZD6738 PK in mice was due to pre-systemic saturation and which appears to be recapitulated clinically at low doses. PK reported here will allow future correlation of tissue related toxicities with drug exposure as well as exposure with immunological responses. These results can also be compared with those from similar studies of other ATRi to contrast drug exposure with responses.

A phase I study of veliparib with cyclophosphamide and veliparib combined with doxorubicin and cyclophosphamide in advanced malignancies

PURPOSE

Veliparib (V), an oral poly(ADP-ribose) polymerase (PARP) inhibitor, potentiates effects of alkylating agents and topoisomerase inhibitors in preclinical tumor models. We conducted a phase I trial of V with iv cyclophosphamide (C) and V plus iv doxorubicin (A) and C.

METHODS

Objectives were to establish the maximum tolerated dose (MTD) of the combinations, characterize V pharmacokinetics (PK) in the presence and absence of C, measure PAR in peripheral blood mononuclear cells (PBMCs) and γH2AX in circulating tumor cells (CTCs). In Group 1, dose escalations of V from 10 to 50 mg every 12 h Days 1-4 plus C 450 to 750 mg/m² Day 3 in 21-day cycles were evaluated. In Group 2, V doses ranged from 50 to 150 mg every 12 h Days 1-4 with AC (60/600 mg/m²) Day 3 in 21-day cycles. In Group 3, patients received AC Day 1 plus V Days 1-7, and in Group 4, AC Day 1 plus V Days 1-14 was given in 21-day cycles to evaluate effects on γH2AX foci.

RESULTS

Eighty patients were enrolled. MTD was not reached for V and C. MTD for V and AC was V 100 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 every 21 days. V PK appears to be dose-dependent and has no effect on the PK of C. Overall, neutropenia and anemia were the most common adverse events. Objective response in V and AC treated groups was 22% (11/49). Overall clinical benefit rate was 31% (25/80). PAR decreased in PBMCs. Percentage of γH2AX-positive CTCs increased after treatment with V and AC.

CONCLUSION

V and AC can be safely combined. Activity was observed in patients with metastatic breast cancer.

Neratinib-Plus-Cetuximab in Quadruple-WT (KRAS, NRAS, BRAF, PIK3CA) Metastatic Colorectal Cancer Resistant to Cetuximab or Panitumumab: NSABP FC-7, A Phase Ib Study

PURPOSE

In metastatic colorectal cancer (mCRC), HER2 (ERBB2) gene amplification is implicated in anti-EGFR therapy resistance. We sought to determine the recommended phase II dose (RP2D) and efficacy of neratinib, a pan-ERBB kinase inhibitor, combined with cetuximab, in patients with progressive disease (PD) on anti-EGFR treatment.

PATIENTS AND METHODS

Twenty-one patients with quadruple-wild-type, refractory mCRC enrolled in this 3+3 phase Ib study. Standard dosage cetuximab was administered with neratinib at 120 mg, 160 mg, 200 mg, and 240 mg/day orally in 28-day cycles. Samples were collected for molecular and pharmacokinetic studies.

RESULTS

Sixteen patients were evaluable for dose-limiting toxicity (DLT). 240 mg was determined to be the RP2D wherein a single DLT occurred (1/7 patients). Treatment-related DLTs were not seen at lower doses. Best response was stable disease (SD) in 7 of 16 (44%) patients. HER2 amplification (chromogenic in situ IHC) was detected in 2 of 21 (9.5%) treatment-naïve tumors and 4 of 16 (25%) biopsies upon trial enrollment (post-anti-EGFR treatment and progression). Compared with matched enrollment biopsies, 6 of 8 (75%) blood samples showed concordance for HER2 CNV in circulating cell-free DNA. Five SD patients had HER2 amplification in either treatment-naïve or enrollment biopsies. Examination of gene-expression, total protein, and protein phosphorylation levels showed relative upregulation of ≥2 members of the HER-family receptors or ligands upon enrollment versus matched treatment-naïve samples.

CONCLUSIONS

The RP2D of neratinib in this combination was 240 mg/day, which was well tolerated with low incidence of G3 AEs. There were no objective responses; SD was seen at all neratinib doses. HER2 amplification, detectable in both tissue and blood, was more frequent post-anti-EGFR therapy.

Abstract 3019: Non-linear absorption pharmacokinetics (PK) of the ATR inhibitor AZD6738 in mice

Introduction: AZD6738 is an inhibitor of the apical kinase Ataxia telangiectasia and Rad-3 related (ATR) and can block induction of DNA damage response signaling cascades that are initiated by ATR following chemotherapy or radiation cancer treatment. AZD6738 is in clinical development and also being used preclinically to mechanistically probe ATR signaling. Currently, little is known about AZD6738 PK, including bioavailability, and tissue distribution, and this information is valuable in both clinical and preclinical settings. Here we describe the intravenous (IV) and oral (PO) PK of AZD6738 in mice.

Methods: Single doses of AZD6738 (IV 10 mg/kg, PO 2.0, 7.5, 20, or 75 mg/kg) were administered to female Balb/c mice. Mice were euthanized from 5 min to 24 h after dosing and plasma and tissues were collected and analyzed by an LC-MS/MS assay modified to include a sulfoxide and sulfone metabolite semiquantitatively. PK parameters and PO bioavailability were determined non-compartmentally (NCA) and compartmentally (CA). Dose linearity was assessed using naively pooled data and statistical comparison of dose normalized Cmax and AUC. ADAPT5 software was used to develop a CA model. Extraction ratio (EH) was calculated from IV administered mice to discern the contribution of hepatic first-pass metabolism to observed bioavailability.

Results: IV data was best described by a two-compartment linear model. Negligible differences were observed between PO half-life at any dose (95.3 to 116 min) compared to the IV half-life (104 min). Increases in PO dose resulted in greater than proportional increases in exposure with statistical differences observed for dose-normalized Cmax and AUC. Concordantly, the bioavailability increased as dose increased, ranging from an F of 31.3% at 2.0 mg/kg to 81.3% at 75 mg/kg. A decrease in Tmax was also observed as dose increased, with a Tmax of 60 min at 2.0 mg/kg and 15 min at all other PO doses. As PO dose increased, decreases in sulfoxide dose-normalized AUC metabolic ratios were observed. A two-compartment model with an absorption compartment containing a saturable component capturing both efflux and first-pass metabolism was developed that adequately described the data with non-linear bioavailability. An empirical Emax fit to bioavailability as a function of dose determined the maximum bioavailability (Emax) to be 87.6% (95%CI 66.7-114%) and Km to be 3.99 (95% CI 1.06-11.3). Comparison of the EH of IV administered mice to the observed 2 mg/kg bioavailability determined ~50% passes the gut wall.

Conclusion:AZD6738 was observed to display saturable intestinal efflux/first-pass metabolism resulting in dose-dependent bioavailability. Increased PO doses yield greater than proportional increases in exposure in mice. Presence of non-linear absorption PK in humans is conjecture.

Funding: TL1TR001858, R50CA211241, P30CA047904 and American Foundation for Pharmaceutical Education, PA DoH Tobacco grant.

Citation Format: Brian F. Kiesel, Jianxia Guo, Christopher J. Bakkenist, Jan H. Beumer. Non-linear absorption pharmacokinetics (PK) of the ATR inhibitor AZD6738 in mice [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3019.

Phase I and pharmacokinetic study of veliparib, a PARP inhibitor, and pegylated liposomal doxorubicin (PLD) in recurrent gynecologic cancer and triple negative breast cancer with long-term follow-up

OBJECTIVE

Poly(ADP-ribosyl) polymerases (PARPs) are nuclear enzymes with roles in DNA damage recognition and repair. PARP1 inhibition enhances the effects of DNA-damaging agents like doxorubicin. We sought to determine the recommended phase two dose (RP2D) of veliparib with pegylated liposomal doxorubicin (PLD) in breast and recurrent gynecologic cancer patients.

METHODS

Veliparib and PLD were administered in a standard phase 1, 3 + 3 dose-escalation design starting at 50 mg veliparib BID on days 1-14 with PLD 40 mg/mg² on day 1 of a 28-day cycle. Dose escalation proceeded in two strata: A (prior PLD exposure) and B (no prior PLD exposure). Patients underwent limited pharmacokinetic (PK) sampling; an expansion PK cohort was added.

RESULTS

44 patients with recurrent ovarian or triple negative breast cancer were enrolled. Median age 56 years; 23 patients BRCA mutation carriers; median prior regimens four. Patients received a median of four cycles of veliparib/PLD. Grade 3/4 toxicities were observed in 10% of patients. Antitumor activity was observed in both sporadic and BRCA-deficient cancers. Two BRCA mutation carriers had complete responses. Two BRCA patients developed oral squamous cell cancers after completing this regimen. PLD exposure was observed to be higher when veliparib doses were > 200 mg BID.

CONCLUSIONS

The RP2D is 200 mg veliparib BID on days 1-14 with 40 mg/m² PLD on day 1 of a 28-day cycle. Anti-tumor activity was seen in both strata. However, given development of long-term squamous cell cancers and the PK interaction observed, efforts should focus on other targeted combinations to improve efficacy.

Phase 1 study of the Aurora kinase A inhibitor alisertib (MLN8237) combined with the histone deacetylase inhibitor vorinostat in lymphoid malignancies

Alisertib, an Aurora kinase A inhibitor, was evaluated in a Phase 1 study in combination with the histone deacetylase inhibitor vorinostat, in patients with relapsed/refractory lymphoid malignancies (N = 34; NCT01567709). Patients received alisertib plus vorinostat in 21-day treatment cycles with escalating doses of alisertib following a continuous or an intermittent schedule. All dose-limiting toxicities (DLTs) were hematologic and there were no study-related deaths. The recommended phase 2 dose (RP2D) of the combination was 20 mg bid of alisertib and 200 mg bid of vorinostat on the intermittent schedule. A 13-patient expansion cohort was treated for a total of 18 patients at the RP2D. There were no DLTs at the RP2D, and toxicities were mainly hematologic. Two patients with DLBCL achieved a durable complete response, and two patients with HL achieved partial response. Alisertib plus vorinostat showed encouraging clinical activity with a manageable safety profile in heavily pretreated patients with advanced disease.

A phase I pharmacokinetic study of belinostat in patients with advanced cancers and varying degrees of liver dysfunction

AIMS

The histone deacetylase inhibitor belinostat has activity in various cancers. Because belinostat is metabolized by the liver, reduced hepatic clearance could lead to excessive drug accumulation and increased toxicity. Safety data in patients with liver dysfunction are needed for this drug to reach its full potential in the clinic.

METHODS

We performed a phase 1 trial to determine the safety, maximum tolerated dose (MTD) and pharmacokinetics of belinostat in patients with advanced cancer and varying degrees of liver dysfunction.

RESULTS

Seventy-two patients were enrolled and divided into cohorts based on liver function. In patients with mild dysfunction, the MTD was the same as the recommended phase 2 dose (1000 mg/m2 /day). Belinostat was well tolerated in patients with moderate and severe liver dysfunction, although the trial was closed before the MTD in these cohorts could be determined. The mean clearance of belinostat was 661 mL/min/m2 in patients with normal liver function, compared to 542, 505 and 444 mL/min/m2 in patients with mild, moderate and severe hepatic dysfunction. Although this trial was not designed to assess clinical activity, of the 47 patients evaluable for response, 13 patients (28%) experienced stable disease.

CONCLUSION

While a statistically significant difference in clearance indicates increased belinostat exposure with worsening liver function, no relationship was observed between belinostat exposure and toxicity. An assessment of belinostat metabolites revealed significant differences in metabolic pathway capability in patients with differing levels of liver dysfunction. Further studies are needed to establish formal dosing guidelines in this patient population.

Phase I trial of belinostat in combination with 13-cis-retinoic acid in advanced solid tumor malignancies: a California Cancer Consortium NCI/CTEP sponsored trial

PURPOSE

The reported maximum tolerated dose (MTD) of single-agent belinostat is 1000 mg/m² given days 1-5, every 21 days. Pre-clinical evidence suggests histone deacetylase inhibitors enhance retinoic acid signaling in a variety of solid tumors. We conducted a phase I study of belinostat combined with 50-100 mg/m²/day 13-cis-retinoic acid (13-cRA) in patients with advanced solid tumors.

METHODS

Belinostat was administered days 1-5 and 13-cRA days 1-14, every 21 days. Dose-limiting toxicity (DLT) was defined as cycle 1 hematologic toxicity grade ≥ 3 not resolving to grade ≤ 1 within 1 week or non-hematologic toxicity grade ≥ 3 (except controlled nausea and vomiting and transient liver function abnormalities) attributable to belinostat.

RESULTS

Among 51 patients, two DLTs were observed: grade 3 hypersensitivity with dizziness and hypoxia at 1700 mg/m²/day belinostat with 100 mg/m²/day 13-cRA, and grade 3 allergic reaction at 2000 mg/m²/day belinostat with 100 mg/m²/day 13-cRA. The MTD was not reached. Pharmacokinetics of belinostat may be non-linear at high doses. Ten patients had stable disease, including one with neuroendocrine pancreatic cancer for 56 cycles, one with breast cancer for 12 cycles, and one with lung cancer for 8 cycles. Partial responses included a patient with keratinizing squamous cell carcinoma of the tonsils, and a patient with lung cancer.

CONCLUSIONS

The combination of belinostat 2000 mg/m² days 1-5 and 13-cRA 100 mg/m² days 1-14, every 21 days, was well-tolerated and an MTD was not reached despite doubling the established single-agent MTD of belinostat.

Safety and Efficacy of T-DM1 Plus Neratinib in Patients With Metastatic HER2-Positive Breast Cancer: NSABP Foundation Trial FB-10

PURPOSE

Patients with human epidermal growth factor receptor 2 (HER2)–positive metastatic breast cancer eventually develop resistance to dual-antibody therapy with trastuzumab plus pertuzumab. Mechanisms of resistance have not been well elucidated. We evaluated the safety, tolerability, and efficacy of ado-trastuzumab emtansine (T-DM1) plus neratinib in patients who progressed on trastuzumab plus pertuzumab.

PATIENTS AND METHODS

In this 3 + 3 dose-escalation study, patients with metastatic breast cancer who progressed on trastuzumab, pertuzumab, and a taxane were treated with T-DM1 at 3.6 mg/kg intravenously every 3 weeks and dose-escalating neratinib at 120, 160, 200, or 240 mg/d orally.

RESULTS

Twenty-seven patients were treated across four dose-levels of neratinib. Dose-limiting toxicity in cycle 1 was grade 3 diarrhea in six patients and grade 3 nausea in one; no patient experienced grade 4 diarrhea, and there were no grade 5 toxicities. Other grade 3 to 4 toxicities included nausea (11%), dehydration (11%), electrolyte abnormality (19%), thrombocytopenia (15%), elevated transaminase levels (7%), and fatigue (7%). Twelve (63%) of 19 evaluable patients had an objective response. Responses occurred at all neratinib doses. Plasma cell–free DNA at baseline showed ERBB2 (HER2) amplification in 10 of 27 patients. Deep and more durable responses occurred in patients with cell-free DNA ERBB2 amplification. Two complete responders had high expression of total HER2 and p95HER2 in baseline tissue.

CONCLUSION

We report the recommended phase II dose of T-DM1 3.6 mg/kg and neratinib 160 mg/d for this combination. Possible resistance mechanisms to HER2 antibodies may be loss of the HER2 receptor and high expression of p95HER2. These data provide the basis for an ongoing phase II study to better define the activity of this regimen.

Abstract PD3-04: Analysis of ERBB2 (HER2) amplification by ctDNA in a phase Ib dose-escalation trial evaluating trastuzumab emtansine (T-DM1) with neratinib in women with metastatic disease with initially diagnosed HER2+ breast cancer: NSABP FB-10

Background:

In this phase Ib study, the activity of T-DM1 plus N was assessed in patients (pt) previously treated with trastuzumab, pertuzumab, and a taxane (H+P+T). Several mechanisms of resistance have been hypothesized in pts progressing following H+P+T, including acquired alterations in the ERBB (HER) family proteins, reactivation of bypass or parallel pathways, or selective elimination of HER2-overexpressing clones. Loss of HER2 amp has been shown to occur in 25-35% of pts with residual tumor after neoadjuvant therapy or in metastatic disease after initial therapy with chemotherapy and HER2-targeted agents. Data on concordance of HER2 status between tissue and blood is limited. In 7 pts with cfDNA HER2 amp, concomitant tissue was concordant in all 7 pairs and response to anti-HER2 therapy occurred in 6. In our study we have retrospectively analyzed cfDNA in blood samples obtained at study entry.

Methods:

Eligible pts had prior H+P+T as neoadjuvant therapy, or 1st-line metastatic disease, measurable disease, ECOG PS ≤2, and adequate hematologic, renal, and liver function. Pts with stable brain metastases were eligible. Treatment consisted of T-DM1 3.6 mg/kg iv q3wk and N 120, 160, 200, or 240 mg/d using a 3+3 dose-escalation design. HER2+ was determined at initial diagnosis; tissue confirmation at study entry (after H+P+T progression) was not required. Blood was collected in for pharmacokinetic analyses of N peak and trough, and for cfDNA using the Guardant360 assay, which is a 73-gene next-generation cfDNA-sequencing panel that detects SNVs, indels, CNAs, and fusions, utilizing Digital Sequencing and custom bioinformatics methods for error correction. The cut-off for HER2 amp was a copy number of ≥2.0 established by Guardant based on training-set data.

Results:

There were 27 H+P+T-resistant pts enrolled and all pts had a blood sample analyzed for HER2 amp. Eighteen pts were evaluable for efficacy at 6 wks and 11 pts at 12 wks. Dose-limiting toxicity occurred in 6 pts during cycle 1, 1 pt was withdrawn for non-compliance, and 2 pts were withdrawn for disease complications. The recommended phase II dose of N was determined to be 160 mg/d. Responses were seen at all dose-levels of N. Pharmacokinetic analyses did not show a clear relationship with either peak or trough and dose-level. Ten pts showed HER2 amp in blood and 17 were non-amp. Of 18 pts evaluable after 2 cycles (6 wks), 12 pts had an objective response (7 amp; 5 non-amp) and 5 had progressive disease (1 amp; 4 non-amp). At 12 wks, there were 3 CRs and 8 PRs (7 amp; 4 non-amp). All CRs were in amp pts and lasted 364, 510, and 859+ days.

Conclusions:

HER2 amp as determined by cfDNA was found in 10 of 27 pts. The deeper and more prolonged (>12 wk) responses occurred in 7 of 10 amp HER2 pts v 4 of 17 non-amp HER2 pts (p=0.04). In our ongoing phase II study of this regimen concomitant tissue and blood will be analyzed to better understand potential benefit or lack of benefit, with continued use of anti-HER2 therapy after progression on anti-HER2 therapies.

Support: Puma Biotechnology, Inc.

Citation Format: Abraham J, Puhalla SL, Sikov WM, Montero AJ, Salkeni MA, Razaq WA, Beumer JH, Kiesel BF, Buyse ME, Adamson LM, Srinivasan A, Pogue-Geile KL, Allegra CJ, Nagy RJ, Jacobs SA. Analysis of ERBB2 (HER2) amplification by ctDNA in a phase Ib dose-escalation trial evaluating trastuzumab emtansine (T-DM1) with neratinib in women with metastatic disease with initially diagnosed HER2+ breast cancer: NSABP FB-10 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD3-04.

Population pharmacokinetics and exposure-response assessment of veliparib co-administered with temozolomide in patients with myeloid leukemias

PURPOSE

Veliparib is an oral inhibitor of poly(ADP-ribose) polymerase enzyme. Combination of veliparib and temozolomide was well-tolerated and demonstrated clinical activity in older patients with relapsed or refractory acute myeloid leukemia (AML) or AML arising from pre-existing myeloid malignancies. We aimed to perform quantitative assessments of pharmacokinetics, efficacy, and safety of veliparib in this patient population to inform future trial design.

METHODS

Population pharmacokinetic analysis was performed using Phoenix^® NLME with pharmacokinetic data obtained from 37 subjects after oral administration of veliparib in a Phase I study with and without temozolomide. Effect of covariates (age, sex, BMI, creatinine clearance (CL_CR), and co-administration of temozolomide) on the pharmacokinetics of veliparib were evaluated, as well as impact of veliparib exposure on mucositis (dose-limiting toxicity), objective response rate (ORR), and overall survival.

RESULTS

A two-compartment model with first-order elimination and a first-order absorption with lag-time adequately described veliparib pharmacokinetics. CL_CR and body weight were clinically significant covariates for veliparib disposition. The proportion of subjects with all grade mucositis increased with veliparib exposure (AUC). However, no trend in ORR and overall survival was observed with increasing exposure.

CONCLUSIONS

Veliparib with temozolomide presents a promising combination for older patients with myeloid leukemias. An exposure-safety relationship was established for this combination. Further clinical investigations aimed at elucidating the veliparib exposure-efficacy/safety relationship and optimizing dosing recommendations for maximizing benefit-risk in patients with advanced myeloid malignancies should study veliparib doses ranging up to 120 mg in combination with temozolomide.

ATR kinase inhibitor AZD6738 potentiates CD8+ T cell-dependent antitumor activity following radiation

DNA-damaging chemotherapy and radiation therapy are integrated into the treatment paradigm of the majority of cancer patients. Recently, immunotherapy that targets the immunosuppressive interaction between programmed death 1 (PD-1) and its ligand PD-L1 has been approved for malignancies including non-small cell lung cancer, melanoma, and head and neck squamous cell carcinoma. ATR is a DNA damage-signaling kinase activated at damaged replication forks, and ATR kinase inhibitors potentiate the cytotoxicity of DNA-damaging chemotherapies. We show here that the ATR kinase inhibitor AZD6738 combines with conformal radiation therapy to attenuate radiation-induced CD8+ T cell exhaustion and potentiate CD8+ T cell activity in mouse models of Kras-mutant cancer. Mechanistically, AZD6738 blocks radiation-induced PD-L1 upregulation on tumor cells and dramatically decreases the number of tumor-infiltrating Tregs. Remarkably, AZD6738 combines with conformal radiation therapy to generate immunologic memory in complete responder mice. Our work raises the possibility that a single pharmacologic agent may enhance the cytotoxic effects of radiation while concurrently potentiating radiation-induced antitumor immune responses.

LC-MS/MS assay for the quantitation of the ribonucleotide reductase inhibitor triapine in human plasma

The ribonucleotide reductase inhibitor and radiosensitizer triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP), NSC 663249) is clinically being evaluated via the intravenous (IV) route for the treatment of cervical and vulvar cancer in combination with primary cisplatin chemoradiation. The need for a 2-h infusion and frequent administration of triapine is logistically challenging, prompting us to pursue oral (PO) administration. In support of the clinical trial investigating oral triapine in combination with chemoradiation, we developed and validated a novel LC-MS/MS assay for the quantification of triapine in 50μL human plasma. After protein precipitation, chromatographic separation of the supernatant was achieved with a Shodex ODP2 column and an isocratic acetonitrile-water mobile phase with 10% ammonium acetate. Detection with an ABI 4000 mass spectrometer utilized electrospray positive mode ionization. The assay was linear from 3 to 3,000ng/mL and proved to be accurate (97.1-103.1%) and precise (<7.4% CV), and met the U.S. FDA guidance for bioanalytical method validation. This LC-MS/MS assay will be an essential tool to further define the pharmacokinetics and oral bioavailability of triapine.

LC-MS/MS assay for the quantitation of the ATR kinase inhibitor VX-970 in human plasma

DNA damaging chemotherapy and radiation are widely used standard-of-care modalities for the treatment of cancer. Nevertheless, the outcome for many patients remains poor and this may be attributed, at least in part, to highly effective DNA repair mechanisms. Ataxia-telangiectasia mutated and Rad3-related (ATR) is a key regulator of the DNA-damage response (DDR) that orchestrates the repair of damaged replication forks. ATR is a serine/threonine protein kinase and ATR kinase inhibitors potentiate chemotherapy and radiation. The ATR kinase inhibitor VX-970 (NSC 780162) is in clinical development in combination with primary cytotoxic agents and as a monotherapy for tumors harboring specific mutations. We have developed and validated an LC-MS/MS assay for the sensitive, accurate and precise quantitation of VX-970 in human plasma. A dilute-and-shoot method was used to precipitate proteins followed by chromatographic separation with a Phenomenex Polar-RP 80Å (4μm, 50×2mm) column and a gradient acetonitrile-water mobile phase containing 0.1% formic acid from a 50μL sample volume. Detection was achieved using an API 4000 mass spectrometer using electrospray positive ionization mode. The assay was linear from 3 to 5,000ng/mL, proved to be accurate (94.6-104.2%) and precise (<8.4% CV), and fulfilled criteria from the FDA guidance for bioanalytical method validation. This LC-MS/MS assay will be a crucial tool in defining the clinical pharmacokinetics and pharmacology of VX-970 as it progresses through clinical development.

LC-MS/MS assay for the simultaneous quantitation of the ATM inhibitor AZ31 and the ATR inhibitor AZD6738 in mouse plasma

The ATM kinase inhibitor AZ31 and ATR kinase inhibitor AZD6738 are in various phases of preclinical and clinical evaluation for their ability to potentiate chemoradiation. To support the preclinical evaluation of their pharmacokinetics, we developed and validated an LC-MS/MS assay for the simultaneous quantification of AZ31 and AZD6738 in mouse plasma. A "dilute and shoot" method was used to precipitate proteins from a sample volume of 50μL. Chromatographic separation was achieved using a Phenomenex Polar-RP column and a gradient mobile phase consisting of methanol-water with 0.1% formic acid. Detection was accomplished using a Waters Quattro Micro mass spectrometer in positive ionization mode. The assay utilizing 50μL sample was linear from 10 to 5000ng/mL and determined to be both accurate (-8.2 to 8.6%) and precise (<5.4% CV) and achieved the criteria for U.S. FDA guidance for bioanalytical method validation. Quantification was achieved in mouse tissue homogenate using a separate 200μL sample preparation. This LC-MS/MS assay will be essential for determining the tissue distribution and pharmacokinetics in future mouse studies.

Parent-Metabolite Pharmacokinetic Modeling and Pharmacodynamics of Veliparib (ABT-888), a PARP Inhibitor, in Patients With BRCA 1/2-Mutated Cancer or PARP-Sensitive Tumor Types

Veliparib (ABT-888) is a novel oral poly-ADP-ribose polymerase (PARP) inhibitor that is being developed for the treatment of hematologic malignancies and solid tumors. Although the pharmacokinetics of veliparib have been studied in combination with cytotoxic agents, limited information exists regarding the pharmacokinetics (PK) of chronically dosed single-agent veliparib in patients with either BRCA 1/2-mutated cancer or PARP-sensitive tumors. The objectives of the current analysis were to characterize the population pharmacokinetics of veliparib and its primary, active metabolite, M8, and to evaluate the relationship between veliparib and M8 concentrations and poly-ADP-ribose (PAR) level observed in peripheral blood mononuclear cells (PBMCs). Seventy-one subjects contributed with veliparib plasma concentrations, M8 plasma concentrations, and PAR levels in PBMCs. Veliparib and M8 concentrations were modeled simultaneously using a population PK approach. A 2-compartment model with delayed first-order absorption and the elimination parameterized as renal (CL_R /F) and nonrenal clearance (CL_NR /F) adequately described veliparib pharmacokinetics. The pharmacokinetics of the M8 metabolite was described with a 2-compartment model. Creatinine clearance(CL_CR ) and lean body mass (LBM) were identified as significant predictors of veliparib CL_R /F and central volume of distribution, respectively. For a typical subject (LBM, 48 kg; CL_CR , 95 mL/min), total clearance (CL_R /F + CL_NR /F), and central and peripheral volume of distribution for veliparib were estimated as 17.3 L/h, 98.7 L, and 48.3 L, respectively. At least 50% inhibition of PAR levels in PBMCs was observed at dose levels ranging from 50 to 500 mg.

Toxicity, pharmacokinetics and metabolism of a novel inhibitor of IL-6-induced STAT3 activation

PURPOSE

The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) promotes gene transcription involved in cancer, and its activation by IL-6 is found in head and neck squamous cell carcinoma. Four triazolothiadizine STAT3 pathway inhibitors were evaluated to prioritize a single compound for in vivo examination.

METHODS

Metabolic stability in mouse liver microsome incubation was used to evaluate four triazolothiadizine analogues, and UPCDC-10205 was administered to mice IV as single or multiple doses to evaluate toxicity. Single-dose pharmacokinetics (PK), bioavailability and metabolism were studied after IV 4 mg/kg, PO 4 mg/kg, or PO 30 mg/kg suspension in 1% carboxymethyl cellulose. Mice were euthanized between 5 min to 24 h after dosing, and plasma and tissues were analyzed by LC-MS. Non-compartmental PK parameters were determined.

RESULTS

Of the four triazolothiadizine analogues evaluated, UPCDC-10205 was metabolically most stable. The maximum soluble dose of 4 mg/kg in 10% Solutol™ was not toxic to mice after single and multiple doses. PK analysis showed extensive tissue distribution and rapid plasma clearance. Bioavailability was ~5%. A direct glucuronide conjugate was identified as the major metabolite which was recapitulated in vitro.

CONCLUSIONS

Rapid clearance of UPCDC-10205 was thought to be the result of phase II metabolism despite its favorable stability in a phase I in vitro metabolic stability assay. The direct glucuronidation explains why microsomal stability (reflective of phase I metabolism) did not translate to in vivo metabolic stability. UPCDC-10205 did not demonstrate appropriate exposure to support efficacy studies in the current formulation.

LC-MS/MS assay for the quantitation of the tyrosine kinase inhibitor neratinib in human plasma

Neratinib is an orally available tyrosine kinase inhibitor targeting HER2 (ERBB2) and EGFR (ERBB). It is being clinically evaluated for the treatment of breast and other solid tumors types as a single agent or in combination with other chemotherapies. In support of several phase I/II clinical trials investigating neratinib combinations, we developed and validated a novel LC-MS/MS assay for the quantification of neratinib in 100μL of human plasma with a stable isotopic internal standard. Analytes were extracted from plasma using protein precipitation and evaporation of the resulting supernatant followed by resuspension. Chromatographic separation was achieved using an Acquity UPLC BEH Shield RP18 column and a gradient methanol-water mobile phase containing 10% ammonium acetate. An ABI 4000 mass spectrometer and electrospray positive mode ionization were used for detection. The assay was linear from 2 to 1,000ng/mL and proved to be accurate (98.9-106.5%) and precise (<6.2%CV), and met the FDA guidance for bioanalytical method validation. This LC-MS/MS assay will be an essential tool to further define the pharmacokinetics of neratinib.

Abstract 2083: Toxicity, bioavailability, pharmacokinetics, tissue distribution and metabolism of a novel small molecule inhibitor of IL-6-induced STAT3 activation

Introduction: The oncogenic transcription factor STAT3 is frequently hyper-activated in head and neck cancer and promotes gene transcription involved in cancer development, maintenance and progression. Several selective small molecule inhibitors of IL-6-induced STAT3 activation were identified in a screening campaign, and four analogs from a lead optimization series were analyzed. Compound UPCDC10205 was prioritized for in vivo testing to evaluate its toxicity, pharmacokinetics (PK) and metabolism in mice.

Methods: The four inhibitors of IL-6-induced STAT3 activation were incubated with liver microsomes from Foxn1 +/nu mice up to 90 min. An LC-MS/MS assay was developed to quantify substrate depletion. Single IV dose toxicity was determined in male and female Foxn1 +/nu mice at the maximum soluble dose of 4 mg/kg of compound UPCDC10205 in 10% Solutol. In the multiple IV dose study in female mice UPCDC10205 was dosed QDx5 at 4, 2.7, and 1.3 mg/kg/day. During toxicity studies clinical health status was observed daily and body weight was recorded twice weekly for 14 days after treatment, followed by necropsy. To evaluate PK, single doses of UPCDC10205 IV 4 mg/kg, PO IV 4 mg/kg, or PO 30 mg/kg UPCDC10205 suspension in 1% CMC, were administered to groups of female mice. Mice were euthanized from 5 min to 24 h after dosing (n = 3). RBCs, plasma and tissues were collected and stored at -80 °C. UPCDC10205 concentrations were quantified by LC-MS/MS. Non-compartmental PK were evaluated. LC-MS/MS was used to screen for metabolites in plasma and urine.

Results: Approximately 80% of compound UPCDC10205 remained after a 90 min microsomal incubation compared to &lt;50% for the other analogs. Mice exhibited no signs of toxicity after single or multiple doses of 4 mg/kg IV. Exposure in liver, lungs, kidney, skeletal muscle and brain were 1.6-3.2-fold that of plasma. Plasma AUC after IV 4 mg/kg (1022 ng/mL*h) compared to PO 4 mg/kg dosing (53 ng/mL*h) yielding a bioavailability of ∼5%. Compound UPCDC10205 was not detected beyond 6 h in any tissue. The plasma half-life was 0.6 h, clearance 3.9 L/h/kg and distribution volume 3.4 L/kg. The major metabolite identified in both plasma and urine was UPCDC10205 N-glucuronide

Conclusion: In vitro, UPCDC10205 was metabolically stable. No gross toxicity was observed in mice administered the maximum soluble dose. UPCDC10205 was widely distributed into tissues and cleared rapidly. Bioavailability was ∼5%. In vivo metabolism of UPCDC10205 was by direct glucuronidation, explaining why microsomal stability (reflective of phase I metabolism) did not translate to in vivo metabolic stability.

Support: P30CA047904; P50CA097190

Citation Format: Brian F. Kiesel, Robert A. Parise, Jianxia Guo, Donna M. Huryn, Paul A. Johnston, Rafaelle Colombo, Malabika Sen, Jennifer Grandis, Julie L. Eiseman, Jan H. Beumer. Toxicity, bioavailability, pharmacokinetics, tissue distribution and metabolism of a novel small molecule inhibitor of IL-6-induced STAT3 activation. [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 2083.

Phase I Study of Veliparib (ABT-888) Combined with Cisplatin and Vinorelbine in Advanced Triple-Negative Breast Cancer and/or BRCA Mutation-Associated Breast Cancer

PURPOSE

Cisplatin is synergistic with vinorelbine and the PARP inhibitor veliparib, and has antineoplastic activity in triple-negative breast cancer (TNBC) and BRCA mutation-associated breast cancer. This phase I study assessed veliparib with cisplatin and vinorelbine.

EXPERIMENTAL DESIGN

A 3+3 dose-escalation design evaluated veliparib administered twice daily for 14 days with cisplatin (75 mg/m(2) day 1) and vinorelbine (25 mg/m(2) days 1, 8) every 21 days, for 6 to 10 cycles, followed by veliparib monotherapy. Pharmacokinetics, measurement of poly(ADP-ribose) in peripheral blood mononuclear cells, and preliminary efficacy were assessed. IHC and gene-expression profiling were evaluated as potential predictors of response.

RESULTS

Forty-five patients enrolled in nine dose cohorts plus five in an expansion cohort at the highest dose level and recommended phase II dose, 300 mg twice daily. The MTD of veliparib was not reached. Neutropenia (36%), anemia (30%), and thrombocytopenia (12%) were the most common grade 3/4 adverse events. Best overall response for 48 patients was radiologic response with 9-week confirmation for 17 (35%; 2 complete, 15 partial), and stable disease for 21 (44%). Germline BRCA mutation presence versus absence was associated with 6-month progression-free survival [PFS; 10 of 14 (71%) vs. 8 of 27 (30%), mid-P = 0.01]. Median PFS for all 50 patients was 5.5 months (95% confidence interval, 4.1-6.7).

CONCLUSIONS

Veliparib at 300 mg twice daily combined with cisplatin and vinorelbine is well tolerated with encouraging response rates. A phase II randomized trial is planned to assess veliparib's contribution to cisplatin chemotherapy in metastatic TNBC and BRCA mutation-associated breast cancer. Clin Cancer Res; 22(12); 2855-64. ©2016 AACR.

Human hepatocyte assessment of imatinib drug-drug interactions - complexities in clinical translation

AIM

Inducers and inhibitors of CYP3A, such as ritonavir and efavirenz, may be used as part of the highly active antiretroviral therapy (HAART) to treat HIV patients. HIV patients with chronic myeloid leukemia or gastrointestinal stromal tumour may need imatinib, a CYP3A4 substrate with known exposure response-relationships. Administration of imatinib to patients on ritonavir or efavirenz may result in altered imatinib exposure leading to increased toxicity or failure of therapy, respectively. We used primary human hepatocyte cultures to evaluate the magnitude of interaction between imatinib and ritonavir/efavirenz.

METHODS

Hepatocytes were pre-treated with vehicle, ritonavir, ketoconazole, efavirenz or rifampicin, and the metabolism of imatinib was characterized over time. Concentrations of imatinib and metabolite were quantitated in combined lysate and medium, using LC-MS.

RESULTS

The predicted changes in imatinib CLoral (95% CI) with ketoconazole, ritonavir, rifampicin and efavirenz were 4.0-fold (0, 9.2) lower, 2.8-fold (0.04, 5.5) lower, 2.9-fold (2.2, 3.5) higher and 2.0-fold (0.42, 3.5) higher, respectively. These predictions were in good agreement with clinical single dose drug-drug interaction studies, but not with reports of imatinib interactions at steady-state. Alterations in metabolism were similar after acute or chronic imatinib exposure.

CONCLUSIONS

In vitro human hepatocytes predicted increased clearance of imatinib with inducers and decreased clearance with inhibitors of CYP enzymes. The impact of HAART on imatinib may depend on whether it is being initiated or has already been dosed chronically in patients. Therapeutic drug monitoring may have a role in optimizing imatinib therapy in this patient population.

LC-MS/MS assay for the quantitation of the HDAC inhibitor belinostat and five major metabolites in human plasma

The histone deacetylase inhibitor belinostat is being evaluated clinically as a single agent in the treatment of peripheral T-cell lymphomas and in combination with other anticancer agents to treat a wide range of human cancers including acute leukemias and solid tumors. To determine the pharmacokinetics of belinostat in the NCI ODWG liver dysfunction study, we developed and validated an LC-MS/MS assay for the quantitation of belinostat and five major metabolites in 0.05 mL human plasma. After protein precipitation, chromatographic separation was achieved with a Waters Acquity BEH C18 column and a linear gradient of 0.1% formic acid in acetonitrile and water. Detection with an ABI 4000Q mass spectrometer utilized both electrospray positive and negative mode ionization. The assay was linear from 30 to 5000 ng/mL for all six analytes and proved to be accurate (92.0-104.4%) and precise (CV <13.7%), and fulfilled FDA criteria for bioanalytical method validation. We demonstrated the suitability of this assay for measuring parent drug and five major metabolites in plasma from a patient who was administered belinostat IV at a dose of 400 mg/m(2). The LC-MS/MS assay that has been developed will be an essential tool to further define the metabolism and pharmacology of belinostat in the ongoing liver organ dysfunction as well as other studies that investigate belinostat with other anticancer agents.