Abstract P4-14-21: A phase I trial of ganetespib (heat shock protein 90 inhibitor) in combination with paclitaxel and trastuzumab in patients with human epidermal growth factor receptor-2 positive (HER2+) metastatic breast cancer (MBC)

Introduction: Targeted therapies in HER2+ MBC significantly improve outcomes but efficacy is limited by therapeutic resistance. HSP90 is a molecular chaperone involved in the stability and function of multiple signaling onco-proteins. HER2 is an acutely sensitive HSP90 client and HSP90 inhibition can overcome trastuzumab resistance. Our group reported objective responses with 17-AAG plus trastuzumab in HER2+ MBC. Ganetespib, a synthetic, second generation HSP90 inhibitor has increased potency and tolerability compared with earlier agents. We reported anti-tumor activity in metastatic HER2+ and triple negative breast cancer with single agent ganetespib. Preclinically, HSP90 inhibition has synergistic anti-tumor activity with taxanes and trastuzumab. This study will define the MTD and RP2D of ganetespib plus paclitaxel and trastuzumab in HER2+ MBC.

Methods: In this 3+3 phase I dose escalation study, patients with trastuzumab-resistant HER2+ MBC receive weekly trastuzumab and paclitaxel (80mg/m2) with ganetespib on day 1, 8, 15 of a 28 day cycle. HR+ positive patients are required to have at least one prior line of endocrine therapy. DLT of ganetespib monotherapy is diarrhea and therefore patients receive prophylactic anti-motility agents. Based on prior experience with ganetespib plus docetaxel in NSCLC, only 3 dose levels of ganetespib were explored: 100mg/m2, 150mg/m2 and a 3rd cohort of 125mg/m2, if needed. Secondary endpoints include evaluation of effects of ganetespib on the pharmacokinetics (PK) of paclitaxel and preliminary efficacy assessment.

Results: The dosing cohorts (100 mg/m2 (n=3) and 150 mg/m2 (n=6)) have been completed without any DLTs. Median age was 46 years (range 29-65), median prior lines of chemotherapy and anti-HER2 therapy were 3 (range 2-6) and 3 (range 2-4) respectively, including prior pertuzumab in 9/9 and T-DM1 in 8/9 patients. There were no grade 3/4 adverse events (AEs) related to ganetespib. Most common AEs related to ganetespib were diarrhea, fatigue, anemia and rash. Paclitaxel PK data available from 6/9 patients are not appreciably different from those reported in literature. Overall response rate was 25% (2/8 had PR in 150 mg/m2 cohort; 1 patient was not evaluable), SD in 63% (5/8), and clinical benefit rate (CR+PR+SD>24 weeks) was 50% (4/8). 3 patients remain on study.

Conclusion: The RP2D of ganetespib is 150mg/m2 in combination with paclitaxel and trastuzumab. The combination was safe and well tolerated. Updated PFS and PK data will be presented. Despite prior taxanes, pertuzumab and T-DM1, clinical activity of this triplet regimen in this heavily pre-treated cohort is very promising and together with our prior experience with 17-AAG plus trastuzumab and single agent ganetespib warrants further study in HER2+ MBC. A phase 2 trial is being planned in trastuzumab-refractory HER2+ MBC who have progressed on prior pertuzumab and T-DM1. Additionally, the protocol is amended to assess the safety of ganetespib in combination with paclitaxel, trastuzumab and pertuzumab in the first-line setting.

Citation Format: Jhaveri K, Teplinsky E, Chandarlapaty S, Solit D, Cadoo K, Speyer J, D'Andrea G, Adams S, Patil S, Haque S, Friedman K, Neville D, Esteva F, Hudis C, Modi S. A phase I trial of ganetespib (heat shock protein 90 inhibitor) in combination with paclitaxel and trastuzumab in patients with human epidermal growth factor receptor-2 positive (HER2+) metastatic breast cancer (MBC). [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 P4-14-21.

A phase Ib trial of IPI-504 (retaspimycin hydrochloride), a novel Hsp90 inhibitor, in combination with docetaxel

3547

Background: IPI-504 is a water-soluble heat shock protein 90 (Hsp90) inhibitor. IPI-504 causes the degradation of a variety of mutated or amplified oncoproteins, including epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2). The combination of IPI-504 and docetaxel demonstrates additive efficacy in murine xenograft models. This Phase 1b trial was undertaken to identify the maximum tolerated dose (MTD) of IPI-504 in combination with docetaxel. Methods: Eligible patients (pts) had advanced solid tumors that were either refractory to available therapies or for which docetaxel alone was an appropriate therapy. Intravenous (IV) 75 mg/m2 docetaxel was given once every three weeks (q 3- weekly). IPI-504 was administered IV q 3-weekly, with 3 pts per cohort and inter-cohort dose escalation. All pts were evaluated for safety, pharmacokinetics (PK), and tumor response. Results: 16 pts have been enrolled at 3 dose levels of IPI-504 (7 at 300 mg/m2, 6 at 450 mg/m2, and 3 at 550 mg/m2). 6 pts had non-small cell lung cancer (NSCLC). Median age was 59 yrs (range 33–77). Median number of cycles received was 3 (1–11), with 5 pts currently on study. There have been 4 dose-limiting toxicities (DLTs): 1 at 300 mg/m2 (Grade 3 febrile neutropenia); 1 at 450 mg/m2 (Grade 3 fatigue); and 2 at 550 mg/m2 (Grade 1 asymptomatic sinus bradycardia requiring hospitalization for observation, and Grade 3 elevated AST with Grade 3 acute respiratory distress syndrome). All DLTs resolved on trial. No PK interactions between docetaxel and IPI-504 have been observed. The regimen of IPI-504 450 mg/m2 with docetaxel 75 mg/m2 has been identified as the recommended phase 2 dose on a q 3-weekly schedule. Conclusions: In this Phase 1b trial, the MTD of IPI-504 plus docetaxel q 3-weekly was identified. Toxicities were reversible and similar to those seen with docetaxel or IPI-504 alone in this patient population. Given the activity of single-agent IPI-504 against NSCLC and the standard use of docetaxel in that disease, an expanded evaluation of this regimen in pts with previously treated NSCLC is on-going. The combination of IPI-504 and docetaxel on a weekly schedule is also being explored.

[Table: see text]

Phase I/II study of docetaxel and 153Sm for castrate metastatic prostate cancer (CMPC): Summary of dose-escalation cohorts and first report on the expansion cohort

5057

Background: We previously reported (ASCO 2008) that full doses of docetaxel (Tax) and Sm can be repetitively delivered safely using a schedule of q 3 week (wk) Tax and q 6–9 wk Sm. Here we summarize the dose-escalation cohorts and safety/efficacy data from the expansion cohort of 24 pts. Methods: Cohorts of 3–6 pts with CPMC were defined by: 65, 70, 75, 75, 75 mg/m2 of Tax and Sam 0.5, 0.5, 0.5, 0.75, 1 mCi/kg. Each cycle was 6 wks. The expansion cohort used 75 mg/m2 Tax (q 3 wk) and 1 mCi/kg Sm (q 9 wk). Pts with an ANC of grade 0–1 and platelet count of > 100,000/mm3 at the end of cycle 1 received additional cycles until progression or toxicity. Results: 52 pts have been treated. 28 pts were taxane naïve, 11 received previous taxanes but were not refractory, and 13 were taxane refractory. As anticipated, side effects were primarily hematologic. However, the leading cause for treatment termination was disease progression, involving 16/52 (31%) pts, rather than toxicity. 12/52 (23%) pts came off for thrombocytopenia, and 2/52 (4%) pts experienced neutropenic fever. Cohort 3 tolerated the highest cumulative dose and total number of doses of docetaxel (mean of 8 doses, range 4–12; mean total dose 600 mg/m2, range 300–900 mg/m2). Cohort 5 tolerated the highest exposure to Sm (mean of 3 doses, range 1–5). 50 pts are evaluable for response; 22 (44%) achieved a ≥ 50% decline in PSA. 50% of the taxane naïve patients achieved a significant PSA decline, as did 55% of the taxane exposed, and 23% of the taxane refractory pts. Mean time to progression in the taxane naïve, treated, and refractory groups were: 7.5 (range 1.4–22.6), 5.8 (range 0.7–13.7), and 4.3 (range 0.7–11.2) months. Conclusions: This regimen is safe and appears to be active both in taxane naïve and taxane refractory patients, as reflected by favorable toxicity profiles, and rates of significant PSA declines and times to progression. The optimal phase II dose may differ by the population treated. For studies involving taxane naïve patients, the regimen of cohort 3 maximizes docetaxel exposure; for studies of taxane refractory patients, cohort 5 maximizes Sm exposure. Support: EUSA, NIH CA102544.

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PIK3CA and AKT1 mutations are independent in invasive breast cancer

Abstract #1046

Background: The PI3K-AKT pathway is the most commonly altered pathway in invasive breast cancer. Somatic mutation in PIK3CA occurs in 26-30%, while AKT1 mutation was recently noted in 4-8%, other mutations occur rarely in PIK3R1 and PTEN. The prognostic implication of PIK3CA somatic mutation is inconclusive in that moderately sized retrospective studies report differing conclusions. To explain these disparate results our hypothesis is that different PIK3CA mutations impart differences in tumor biology. In an attempt to definitively identify the prognostic importance and functional attributes that specific mutations impart to breast tumor biology we are performing a broad mutation analysis on 600 archival invasive breast tumors with greater than 10 years of follow-up.
 Methods: Archival formalin-fixed paraffin embedded (FFPE) invasive breast tumors were identified from an institutional database from 1992-1996 that had known vital status and primary breast tumor size greater than 1 cm. From the confirmed invasive tumor blocks, two 10µm sections are cut for DNA extraction, punch blocks are obtained for tissue microarray (TMA) construction for immunohistochemistry and clinical demographics are collected. DNA is extracted and quantitated. PIK3CA hotspot mutations and rare PIK3CA mutations less commonly observed but thought to impart an oncogenic phenotype along with the recently identified AKT1 (E17K) mutation are assessed using the Sequenom genome multiplex array. PIK3CA hotspot mutations and AKT1(E17K) are confirmed by additional analysis on an alternate multiplex array. The first 190 cases were also assessed by Sanger sequencing for all PIK3CA coding exons.
 Results: The multiplex arrays used for the Sequenom mutation analyses had been previously validated. Thus far 400 samples have been procured and 190 cases have undergone mutation analysis. Both native DNA and DNA that had undergone whole genome amplification (WGA) were assessed to identify the most informative method for FFPE specimens. Notably, PIK3CA amplification and Sanger sequencing or WGA and mutation analysis by Sequenom multiplex array was less sensitive for identifying mutations than using unamplified native DNA with Sequenom analysis. Native DNA was informative in greater than 98% samples (3/190 uninformative) for the majority of PIK3CA mutations. All samples were informative for the most common hotspot mutation at PIK3CA (H1047R). At this report, the incidence of PIK3CA hotspot mutations (E542K, E545K, H1047R, H1047L) is 26.3% (50/190 cases), with rare PIK3CA mutations (C420R, N345K) occurring in 2.6% of cases. The more recently identified AKT1 (E17K) mutation is identified in 4.2% of cases and occurs independently of those tumors which harbor a PIK3CA mutation.
 Discussion: Mutation analysis, demographic collection and statistical analysis will be completed and updated at the meeting. The work thus far demonstrates that assessment of small amounts of archival tissue can be easily procured and undergo mutation assessment for key mutations that may be targeted therapeutically.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1046.

Extracellular cleaved HER2 (p95) confers partial resistance to trastuzumab but not HSP90 inhibitors in models of HER2 amplified breast cancer

10515

Background: Breast cancers containing an amplified copy of the HER2 receptor tyrosine kinase represent 20–30% of all cases and antibody directed therapy targeting the extracellular domain of HER2 with trastuzumab has proven broadly efficacious. However, resistance to trastuzumab is a common phenomenon. Recent work has identified a cleaved, 95kD version of HER2 that lacks the extracellular epitope in which the trastuzumab binding site is found. Presence of this so called “p95” has been correlated with a worse clinical prognosis. We hypothesized that p95 may enable tumor resistance to trastuzumab. Methods/Results: We established models of p95 expressing breast cancer by transfecting p95 into preexisting models of HER2 amplified breast cancer. We find that cells expressing p95 display increased resistance to the growth inhibitory effects of trastuzumab. The PI3K-AKT pathway that is downregulated by Trastuzumab is less affected in the p95 expressing cells. Furthermore, p95 demonstrates an association with HER3 that is unaffected by trastuzumab treatment. Next, we evaluated the efficacy of therapies targeted against the intracellular domain of HER2 such as the HSP90 inhibitor, 17-AAG. HER2 requires HSP90 for its conformational stability and inhibitors of HSP90 result in growth inhibition of HER2+ breast cancer. We find that p95 displays a similar requirement for HSP90 as inhibitors of HSP90 result in the degradation of p95. Moreover, cells overexpressing p95 are equally susceptible to the antitumor effects of HSP90 inhibitors as those without high levels of p95. Finally, we utilized an empirically derived, in vivo model of trastuzumab resistance that displays high level expression of p95. As with the transfected models, these tumors retain their sensitivity to HSP90 inhibitors as treatment of mice bearing tumors results in both degradation of HER2 and p95 as well as robust tumor growth inhibition. Conclusions: Given the presence of p95 in human breast tumor samples, the data suggest that p95 may play an important role in mediating clinical resistance to trastuzumab. They further suggest that such tumors may retain their sensitivity to targeted therapy against the intracellular portion of HER2 such as with lapatinib or 17-AAG.

No significant financial relationships to disclose.

Phase I study of docetaxel and 153Sm repetitively administered for castrate metastatic prostate cancer (CMPC)

5152

Background: Docetaxel (Tax) prolongs survival in patients (pts) with CMPC. Early clinical data suggest that Tax combined with bone seeking radiopharmaceuticals may improve survival relative to chemotherapy alone. 153Sm-lexidronam (Sam) (Quadramet, Cytogen Inc.) is a radiopharmaceutical with a short T1/2 and a favorable toxicity profile. Methods: Pts with progressive CMPC are treated in cohorts of 3–6. Prior treatment with taxanes is permissible. Cohorts are defined by dose escalations of: Tax 65, 70, 75, 75, 75 mg/m2 and Sam 0.5, 0.5, 0.5, 0.75, 1 mCi/kg. Each cycle is 6 weeks. Tax is given day 1 and 22 and Sam day -1 to 1 of each cycle. DLT is defined as cycle 1 = grade 3 non-hematologic toxicity, grade 3 neutropenia that lasts for >29 days, or grade 3- 4 anemia or thrombocytopenia of = 5 days. Pts with an ANC of grade 0–1 or platelet count (PLT) of >100,000/mm3 at the end of cycle 1 may receive additional cycles. Pts are treated until progression or toxicity. Results: 18 pts have been treated in 5 cohorts of 3 pts to date. 6 pts were treated in cohort 2. Two pts have not yet received enough treatment to be evaluable. DLT has not yet been reached. The mean number of cycles/pt is 3 (range 1–6). As anticipated, toxicities have primarily been hematologic (see table ). Two pts came off study for hematologic toxicity; one in cohort 2 had grade 3 PLT after 5 cycles and has not recovered at >175 days and 1 pt (cohort 2) failed to recover PLT in the allotted time frame during cycle 4 prohibiting further treatment. No other pts required treatment delays for hematologic toxicity. Mean baseline PSA was 294.6ng/ml with 7/16 (44%) pts achieving = 50% decline in PSA. Conclusions: Coadministration of Tax and Sam has been well tolerated. Repetitive dosing is feasible. Standard approved doses of each drug are being tested in the present (and final) cohort. DLT has not yet been reached. Accrual continues, to refine the optimal dose and schedule in preparation for phase II. Support: Cytogen, Inc., NIH CA102544

[Table: see text]

No significant financial relationships to disclose.

Induction of complete regressions of oncogene-induced breast tumors in mice

Over the past decade, mouse models of cancer have come to resemble human disease much more closely than simple subcutaneous or orthotopic systems. Intervention strategies that work on these new model systems are more likely to have an impact clinically. We have shown recently that antiangiogenic stress imposed by loss of Id protein in endothelial progenitor cells results in dramatic central necrosis in breast tumors initiated in mice by overexpression of the her2/neu oncogene. Tumor cells remain viable at the periphery, perhaps via the hypoxic response pathway which allows the lesions to expand. Inhibition of this pathway by the inactivation of the Hif-1alpha chaperone Hsp90 in combination with antiangiogenic stress leads to the first reported complete regression of these aggressive breast tumors.

Phase I trial of KOS-953, a heat shock protein 90 inhibitor, and trastuzumab (T)

501

Background: KOS-953 (17-AAG in Cremophor) is a potent Hsp90 inhibitor that in vivo induces rapid degradation of Her2, loss of pAKT and tumor growth inhibition in a Her2+ breast cancer xenograft. Objectives: Define the phase 2 dose of KOS-953 + T. Define toxicity and PK of KOS-953, its active metabolite and T. Assess changes in intracellular signaling proteins (such as Hsp70) in leucocytes. Describe antitumor activity. Methods: Eligible pts with advanced solid tumors (Her2 + was not required) received standard weekly doses of T followed by IV KOS-953 in escalating doses over 2 hrs. Results: 25 pts enrolled in 4 cohorts (225, 300, 375 and 450 mg/m2; 4, 3, 8 and 10 patients per cohort), receiving a total of 94 cycles (median 3, range <1 - 12+). Demographics: 21 female (17 with Her2+ metastatic breast cancer ‘MBC‘, 1 Her2 status unknown); median age/KPS 66 yrs/90; # prior T-containing regimens for MBC pts (n=18) equaled 2 (range 0–5). DLT was observed at the 3rd and 4th cohort (1 pt each): 2-week dose delay for recovery from Grade 4 fatigue/Grade 2 nausea & anorexia at 375 mg/m2; delayed recovery of platelets at 450 mg/m2. Drug-related Grade 3 toxicity: emesis, increased ALT and hypersensitivity (n=2); Grade 4 drug-induced thrombocytopenia in a pt with Hashimoto’s disease after 7 cycles. In general the drug was well tolerated. Grade 1 or 2 toxicities included fatigue, nausea, diarrhea, emesis, headache, rash/pruritus, increased AST/ALT and anorexia. Most toxicities (except headache) were not dose dependent. PK of parent (n=21): t½ 3.0 ± 2.1 h; clearance 31.8 ± 12.8 L/h; Vz 164 ± 101 L. Metabolite: Tmax 30–60 min after end-of-infusion with similar AUC and longer t½ of 6.1 ± 1.7 h. PK of T showed no changes compared to previous reports. Among 17 pts with Her2 + MBC s/p multiple regimens of T: PR= 1, MR = 3, 5 pts with SD (5, 7+, 9 and 12+ months). Pts with PR and MRs had confirmed progression of disease prior to study on T-containing regimen. Pharmacodynamic testing showed reactive induction of Hsp70/72 in leucocytes at all dose levels. Conclusions: KOS-953 added to T is active in refractory Her2 + MBC with no change in PK compared to single-agent therapy. The phase 2 dose of KOS-953 is 450 mg/m2; enrollment to the phase 2 trial of this combination in Her2+ MBC is on-going.

[Table: see text]

V600E B-Raf requires the Hsp90 chaperone for stability and is degraded in response to Hsp90 inhibitors

The Raf family includes three members, of which B-Raf is frequently mutated in melanoma and other tumors. We show that Raf-1 and A-Raf require Hsp90 for stability, whereas B-Raf does not. In contrast, mutated, activated B-Raf binds to an Hsp90-cdc37 complex, which is required for its stability and function. Exposure of melanoma cells and tumors to the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin results in the degradation of mutant B-Raf, inhibition of mitogen-activated protein kinase activation and cell proliferation, induction of apoptosis, and antitumor activity. These data suggest that activated mutated B-Raf proteins are incompetent for folding in the absence of Hsp90, thus suggesting that the chaperone is required for the clonal evolution of melanomas and other tumors that depend on this mutation. Hsp90 inhibition represents a therapeutic strategy for the treatment of melanoma.

Modulation of Hsp90 function by ansamycins sensitizes breast cancer cells to chemotherapy-induced apoptosis in an RB- and schedule-dependent manner. See: E. A. Sausville, Combining cytotoxics and 17-allylamino, 17-demethoxygeldanamycin: sequence and tumor biology matters, Clin. Cancer Res., 7: 2155-2158, 2001

17-allyl-aminogeldanamycin (17-AAG) is an ansamycin antibiotic that binds to a highly conserved pocket in the Hsp90 chaperone protein and inhibits its function. Hsp90 is required for the refolding of proteins during cellular stress and the conformational maturation of certain signaling proteins. 17-AAG has antitumor activity in cell culture and animal xenograft models and is currently in clinical trial. It causes an RB-dependent G(1) arrest, differentiation, and apoptosis. RB-negative cells arrest in mitosis and undergo apoptosis. Hsp90 plays an important role in the cellular response to environmental stress. Therefore, we tested whether the regulation of Hsp90 function by 17-AAG could sensitize cells to cytotoxic agents. 17-AAG sensitized tumor cells to Taxol and doxorubicin. Taxanes cause growth arrest in mitosis and apoptosis. The addition of 17-AAG to cells after exposure to Taxol significantly increased both the activation of caspases 9 and 3 and apoptosis. In cells with intact RB, exposure to 17-AAG before Taxol resulted in G(1) arrest and abrogated apoptosis. Schedule dependence was not seen in cells with mutated RB, because both agents blocked cells in mitosis. Schedule- or RB-dependence was also not observed when cells were treated with 17-AAG and doxorubicin, a DNA-intercalating agent that acts on different phases of the cell cycle. These findings suggest that inhibition of Hsp90 function by 17-AAG enhances the apoptotic effects of cytotoxic agents. The sequence of drug administration and the RB status significantly influence efficacy.