Combination Regimens of nab-Rapamycin (ABI-009) Effective Against MDA-MB-231 Breast-Tumor Xenografts

Background: The mammalian target of Rapamycin (mTOR) is a key intracellular kinase integrating cell proliferation and survival and is an attractive target for cancer therapy. Nab-rapamycin (ABI-009) was developed using proprietary nab-technology and showed dose-linear pharmacokinetics, safety up to 90 mg/kg and effective antitumor activity at 40 mg/kg in the human-tumor-xenograft panel. The goal of this study was to test the effectiveness of different combination regimens for ABI-009 against MDA-MB-231 breast-tumor xenografts.Materials and methods: Subcutaneous human-breast (MDA-MB-231) tumors were grown in athymic nude mice and treated intravenously (IV) with ABI-009 alone at 40 mg/kg (3xwkly/4wks) and in combination with Erlotinib (50 and 100 mg/kg/day/4wks, IP), Cetuximab (20 and 40 mg/kg, 3xwkly/4wks, IP), Doxorubicin (2 and 5 mg/kg, wkly/10 wks, IV), Oxaliplatin (5 and 10 mg/kg wkly/4 wks, IV), SAHA (50 mg/kg, qdx7 or qdx14, IP), and Perifosine (30 and 60 mg/kg, 3xwkly/4wks, PO). The animal weights and tumor measurements were recorded three times weekly and adverse observations recorded.Results: ABI-009 was highly effective as a single agent against MDA-MB-231 breast tumor xenografts with 75% tumor-growth inhibition (TGI). Combination with Erlotinib resulted in TGI of 85% and 95% (50 and 100 mg/kg, respectively), 83% and 87% for Cetuximab (20 and 40 mg/kg, respectively), 83% and 90% for Doxorubicin (2.5 and 5 mg/kg, respectively), 82% and 85% for Oxaliplatin (5 and 10 mg/kg, respectively), 82% and 90% for SAHA (7 and 14 day treatment, respectively), and 92% and 96% for Perifosine (30 and 60 mg/kg, respectively). Notably, Erlotinib and Perifosine were found to synergize with ABI-009 resulting in maximum TGI and tumor growth delay.Discussion: ABI-009 (nab-rapamycin) alone was highly effective against MDA-MB-231 human-breast-tumor xenografts. Antitumor activity of ABI-009 was significantly increased in combination with kinase inhibitors, Erlotinib (EGFR-kinase inhibitor) and Perifosine (AKT inhibitor). Antitumor activity of ABI-009 was also significantly increased in combination with Doxorubicin – a topoisomerase inhibitor, and SAHA – an HDAC inhibitor, but not in combination with Oxaliplatin – a DNA crosslinker. In contrast, combination of ABI-009 with anti-EGFR monoclonal antibody, Cetuximab was not effective. The synergy of these combinations confirmed that rapamycin is active only on TORC1 and that suppression of TORC2 via AKT or PI3K pathways is a means of increasing activity of mTOR inhibitors with potential relevance to breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6106.

Correlation of SPARC, ER, PR, and HER2 tumor with progression-free survival from a phase II neoadjuvant trial of gemcitabine, epirubicin, and nab-paclitaxel

618

Background: Neoadjuvant combinations of gemcitabine (G), anthracyclines and taxanes have demonstrated substantial activity with pCR rates of 20–25%. Secreted protein acidic rich in cysteine (SPARC) is an albumin binding protein that mediates intratumoral accumulation of nab-paclitaxel (nab-P) via a SPARC-albumin binding activity and is a poor prognostic factor for survival. This study was designed to evaluate the feasibility and safety of a biweekly schedule of neoadjuvant nab paclitaxel (nab-P) with G and epirubicin (E) with SPARC tumor assessments performed in consenting patients (pts). Methods: Eligibility: Clinical T1c-T4d and/or N0–3, M0 breast cancer (T1N0M0 excluded), normal LVEF. ER/PR/HER-2 obtained for all pts. Treatment: neoadjuvant G 2,000 mg/m2, E 50 mg/m2, and nab-P 175 mg/m2 q14 days x 6 cycles followed by surgery. Post operative therapy: G 2,000 mg/m2 and nab-P 220 mg/m2 q14 days x 4 cycles. Myeloid growth factors were mandated with all cycles. Two different antibody reagents were used to probe for SPARC expression of tumoral SPARC and stromal SPARC; level 3 immunohistochemical (IHC) SPARC staining was considered positive. Results: 123 pts enrolled. Pathologic responses are available for 112 pts with 11 unevaluable. 82 pts consented to SPARC tumor testing. Median age 51 (29–72). Median tumor size 4.5 cm. 42% ER-/PR -. 55% clinical T3/T4 and 66% node positive. Pathologic complete responses (pCR) were noted in 22 pts (18%) with PRs in 84 pts (68%), and 6 SD (5%). SPARC IHC staining was available in 77 tumor samples; SPARC positivity was noted in 89% of evaluated tumors achieving pCR. Triple negative, ER negative or PR negative tumors were associated with worse PFS. SPARC + tumors showed a trend to improved PFS that was strongly associated with tumoral SPARC but not stromal SPARC. Conclusions: Dose dense neoadjuvant G, E, and nab-P is active and well tolerated with a favorable pCR rate of 20%. ER neg, PR neg, and triple negative tumors were associated with worse PFS. Despite literature reports of SPARC positivity associated with poor prognosis, SPARC+ tumors in this study showed a high concordance with tumor response and a trend to improved PFS with tumoral SPARC.

[Table: see text]

SPARC correlation with response to gemcitabine (G) plus nab-paclitaxel (nab-P) in patients with advanced metastatic pancreatic cancer: A phase I/II study

4525

Background: Pancreatic cancer cells and surrounding stroma are known to overexpress SPARC (secreted protein acid rich in cysteine), which is associated with poor clinical outcomes. nab-P, an albumin-bound nanoparticle form of paclitaxel increased tumor accumulation of paclitaxel through binding of albumin to SPARC. This disease specific phase 1 study was designed to evaluate the safety and efficacy of G + nab-P and the correlation of response with tumor SPARC and serum CA19–9 levels. Methods: nab-P doses (100–150 mg/m2) + (G) (1000 mg/m2) were given on days 1, 8, and 15 of a 28-day cycle to pts with metastatic pancreatic adenocarcinoma and with no prior chemotherapy for their metastatic disease. Level 3 SPARC staining by immunohistochemistry was considered positive. Results: 63 pts received treatment. The most common grade 3 and 4 adverse event that occurred in >20% of pts was neutropenia. Nine (18%) pts and 4 (8%) pts had a grade 3/4 event, respectively. Neuropathy was also observed. One combination-associated death due to sepsis occurred at the 150 mg/m2 nab-P level. Serial PET scans of 53 pts with outside adjudication to date showed 12 (23%) complete responses, 29 (55%) partial responses (PRs) and 4 (8%) stable disease (SD). By RECIST criteria, of the 49 pts evaluable to date, 1(2%) had CR, 12 (24%) had PR, and 20 (41%) had SD. The median survival was 9 months to date. SPARC data were available for 35 pts, of which 10 (29%) were SPARC+ and 25 (71%) were SPARC-. Of these, 27 pts had evaluable response data. Pts that were SPARC+ (8/27) were more likely to be responders (6/8, 75%) than pts who were SPARC- (5/19, 26%), P = 0.03, Fisher's exact test. Median progression-free survival (PFS) increased from 4.8 months for SPARC- pts (22 pts) to 6.2 months for SPARC+ pts (9 pts); however, these data are still immature. Of 45 pts with elevated CA19–9 at baseline, 42 (93%) had maximum decrease of >40% with a median maximum decrease of 92%. Conclusions: The combination of nab-P and G was generally well tolerated and had substantial enough antitumor activity in patients with pancreatic cancer to warrant a phase III clinical trial. SPARC+ status in these patients was associated with higher response rate and longer PFS.

[Table: see text]

Results of a multicenter pilot study of weekly nab-paclitaxel, carboplatin with bevacizumab, and trastuzumab as neoadjuvant therapy in HER2+ locally advanced breast cancer with SPARC correlatives

527

Background: The addition of targeted therapies to standard chemotherapy has resulted in improved outcomes in metastatic, neoadjuvant and early stage breast cancer. A phase III study in MBC demonstrated improved efficacy with nab paclitaxel (nab-P) compared with standard solvent-based paclitaxel. The secreted protein acidic rich in cysteine (SPARC) is a poor prognostic factor for survival and may mediate enhanced intratumoral accumulation of nab-P via an interaction with albumin. This multicenter phase II pilot study was designed to evaluate the feasibility, safety, and preliminary efficacy of dual VEGF and HER-2 monoclonal antibodies of bevacizumab (B) and trastuzumab (T) administered in with neoadjuvant nab-P and carboplatin (C) with SPARC tumor correlatives. Methods: Eligibility: clinical T1c-T4d and/or N0–3, M0 (T1N0M0 excluded) chemo naive, ECOG PS 0–2, normal LVEF, adequate organ function. Treatment: nab-P 125 mg/m2 D1, 8, 15 with C AUC 6 D1 q28 days plus T 4 mg/kg load followed by 2 mg/kg/wk and B 5 mg/kg/wk x 6 cycles followed by surgery. Post surgery T and B continued for 52 wks. SPARC tumor expression was measured by immunohistochemistry. Results: 29 pts are enrolled and evaluable for safety. Median age: 52 years (29–76), ECOG PS 0–93%, median tumor size 3.2 cm, 54% ER-/PR-, 72% node positive. G3/4 neutropenia was 38% with no febrile neutropenia. Nonheme toxicity: G3/4 hyperglycemia 10%, proteinuria and hypertension, each in 7%. 8 pts were hospitalized (infection-4, ↓LVEF-1, wound dehiscence-1 pt, other-2). 5 pts did not complete neoadjuvant therapy (↓LVEF-1, noncompliance-1, pt request-3) and 10 pts did not complete post op therapy ((pt request-2, toxicity-3, wound-2, unk-3). Pathologic responses are available for 20 pts. pCR was noted in 13/20 pts (65%) and PR was noted in 7/20 pts (35%). 77% of the pCR pts (10/13) and 86% of the PR pts (6/7) were positive for SPARC. Conclusions: Neoadjuvant B, T with nab-P and C is feasible and highly active with a remarkable pCR of 65%. SPARC tumor correlations with pathologic response data reveal a concordance between the high response rate and high incidence of SPARC positivity.

[Table: see text]

Sirolimus-associated lymphoedema: eight new cases and a proposed mechanism

Sirolimus, an inhibitor of the mammalian target of rapamycin (mTOR), is increasingly used as an agent for post-transplant immunosuppression and the treatment of solid organ and haematological malignancies and hamartomas. Its advantages include a lack of nephrotoxicity and a lower incidence of nonmelanoma skin cancers; adverse effects include delayed wound healing, increased lymphocoele formation and rarely lymphoedema. We report a series of eight cases of severe, sustained, unilateral and bilateral lymphoedema in patients receiving sirolimus for post-transplant immunosuppression, classify their lymphoscintigraphy findings and propose a mechanism of aetiology based on the interaction of mTOR with key mediators of lymphangiogenesis.

Evidence of 'genuine empty follicles' in follicular aspirate: a case report

Failure to retrieve oocytes after normal ovarian stimulation has been labeled 'empty follicle syndrome' (EFS). The existence of genuine EFS has been questioned and is still controversial. Here, we report an unusual case in which an extraordinary number of empty follicle-like structures were identified in the ovarian aspirate at the time of retrieval. A 31-year-old woman presented with a 4-year history of primary infertility and underwent ovulation induction. The patient was given hCG and oocyte retrieval was performed 36 h later. During the oocyte retrieval, more than 200 tiny structures resembling pre-antral follicles were noted in the ovarian aspirate. They exhibited two to three layers of granulosa cells and appeared to enclose an immature oocyte. They showed a great variation in size ranging between 40 and 80 microm. These structures were further characterized by electron microscopy and cultivated in vitro to assess hormone secretion. The follicles were found to be devoid of oocytes, but each had a readily identifiable zona. Hormone assays revealed that these follicles were secreting increasing levels of estradiol. A second in vitro fertilization attempt gave similar results. These data are suggestive of some failure in the oocyte maturation process. We speculate that this may be the first actual evidence to support the existence of true empty follicles, which if left to grow in vivo might lead to empty graffian follicles and genuine EFS.

Nanoparticle albumin-bound (nab) IDN5404: a novel vascular disrupting agent with potent antitumor and antiangiogenic effects

Abstract #2138

Background: The tumor vasculature is an established target for the therapy of solid tumors. IDN5404 is a thiocolchicine dimer with antitubulin and topisomerase 1 inhibitor properties. In this study, nab-formulated IDN5404 was examined for antitumor effects in three xenograft models and for antiangiogenic as well as vascular disrupting activity (VDA) in the avian embryonic chorioallantoic membrane (CAM) assays.
 Materials and Methods: Subcutaneous human breast (MX-1 and MDA-MB-231), colon (HT29), and prostate (PC3) tumors were grown in athymic nude mice and treated intravenously (IV) with nab-5404 alone at 10, 20, 30, or 40 mg/kg (q3dx4 or q4dx3) and in combination with IV or intraperitoneal (IP) nab-paclitaxel (Abraxane; 10, 15 or 30 mg/kg, qdx5 or q4dx3). The effect of dose, schedule, and sequence of combination regimen was tested. Nab-5404 was administered 24-hr before, concurrently or 24-hr after Abraxane administration. The effect of nab-5404 on embryonic angiogenesis was examined in vivo using the standard chick CAM assay with 3-day old embryos (n = 18). The quail CAM assay was used to determine the time course of VDA. Quail embryos (n = 36) were exposed to nab-5404 (1 to 16 µg/ml) on day 7 and digital CAM images were acquired over a 60 min period for scoring VDA.
 Results: Significant dose-dependent tumor growth inhibition (TGI) was observed in all xenograft models. In the MX-1 and HT29 models, nab-5404 (30 mg/kg, q3dx4) exhibited potent antitumor activity (P < 0.0001, ANOVA, vs. saline) alone and in combination with Abraxane (TGI for MX-1: 65% and 76%; TGI for HT29: 44% and 74% respectively). Nab-5404 was similarly effective with the q4dx3 schedule. In addition, when Nab-5404 (20 mg/kg, q4dx3) was administered 24-hr before, concurrently or 24-hr after Abraxane (5 mg/kg, q4dx3), the combination resulted in TGI of >99%, 88%, and 72% respectively. Using the in vivo chick CAM assay, nab-5404 inhibited embryonic angiogenesis by over 90% at 5 µg/CAM without affecting viability. Furthermore, rapid collapse of blood vessels was observed within 30 min in the viable quail CAM assay when embryos were exposed to nab-5404 at 4-16 µg/ml.
 Discussion: Nab-5404 alone and in combination with Abraxane demonstrated significant TGI in xenograft models of human breast, colon or prostate cancer. This effect was shown to be due to the rapid VDA of nab-5404. Maximum antitumor activity was seen when nab-5404 was administered 24 hr before Abraxane. Nab-5404, a microtubule-destabilizing vascular disruptive agent, potentiates the cytotoxic effects of nab-paclitaxel, a microtubule-stabilizing agent and the data suggest that these two agents may be utilized effectively in combination.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2138.

Antitumor activity, and antiangiogenic activity of nanoparticle albumin-bound nab-rapamycin in combination with nab-paclitaxel

Abstract #3125

Background: Rapamycin inhibits downstream signals from the mammalian target of rapamycin (mTOR), a known kinase member of a signaling pathway that promotes tumor growth. Rapamycin's poor aqueous solubility and poor chemical stability have limited its development as an intravenous (IV) anticancer agent. Nab-rapamycin utilizes the albumin-bound technology to allow for IV administration of rapamycin and has demonstrated dose-linear pharmacokinetics and safety up to 90 mg/kg with effective antitumor activity at 40 mg/kg against a human panel of tumor xenografts. This study investigated the efficacy of combined therapy with nab-paclitaxel (Abraxane®) utilizing invasive human breast (MDA-MB-231) and colon (HT29) cancer xenograft models.
 Material and Methods: Xenograft transplants using luciferase-tagged MDA-MB-231 cells were implanted into mammary fatpad of SCID mice and allowed to reach 460 mm3 in size prior to IV administration of saline (vehicle, n = 9); nab-rapamycin, 3x wkly for 2 wks at 40 mg/kg (nab-rap-2W; n = 8); nab-rapamycin, 3x wkly for 4 wks at 40 mg/kg (nab-rap-4W; n = 8); Abraxane, qdx5 at 30 mg/kg (ABX; n = 8); nab-rap-2W + ABX (n = 9); or nab-rap-4W + ABX (n = 8). HT29 xenografts were also treated with nab-rap-4W (n = 8) and nab-rap-4W + ABX (10 mg/kg, qdx5, IP, n = 8). The in vivo antiangiogenic effect of nab-rapamycin was evaluated using the standard in vivo chick chorioallantoic membrane (CAM) assay with 3-day old embryos (n = 18).
 Results: Relative to vehicle controls, nab-rap-2W (P < 0.00011), nab-rap-4W (P < 0.0001), and ABX (P < 0.0001) were effective against MDA-MB-231 tumor xenograft models with tumor growth inhibition (TGI) of 60%, 66%, and 73% respectively. Additive antitumor effects were observed with combination of nab-rapamycin + ABX with TGI of 81% and 86% for nab-rap-2W + ABX and nab-rap-4W + ABX groups, respectively. For HT29 tumors, the combination of ABX and nab-rapamycin also showed greater TGI (89%) compared to nab-rapamycin alone (81%). In the chick CAM assay, nab-rapamycin demonstrated antiangiogenic efficacy at doses of 10 µg and above without affecting embryo viability.
 Conclusions: Combination therapy of nab-rapamycin and Abraxane was more effective at inhibiting breast and colon xenograft tumor growth than single therapy of either drug. The enhanced antitumor activity seen with combined nab-rapamycin-Abraxane may in part be due to the observed antiangiogenic activity of nab-rapamycin.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3125.

Preliminary progression free survival and SPARC tumor correlatives from a phase II neoadjuvant trial of gemcitabine, epirubicin, and nab paclitaxel

Abstract #5116

Background: Neoadjuvant combinations of gemcitabine (G), anthracyclines and taxanes have demonstrated significant activity with pCR rates of 20-25% albeit with significant myelosuppression. Secreted protein acidic rich in cysteine (SPARC) is an albumin binding protein that mediates intratumoral accumulation of nab-paclitaxel (nab-P) via a SPARC-albumin specific binding activity. This study was designed to evaluate a biweekly schedule of neoadjuvant nab paclitaxel (nab-P) with gemcitabine and epirubicin (E). SPARC tumor assessments were performed in consenting patients (pts) with subsequent pathologic and survival correlatives.
 Methods: Eligibility: Clinical T1c-T4d and/or N0-3, M0 breast cancer (T1N0M0 excluded), ECOG PS 0-2, normal LVEF. ER/PR/HER2 obtained for all pts. Treatment: 6 cycles neoadjuvant G 2000 mg/m2, E 50 mg/m2, and nab-P 175 mg/m2 q14 days followed by surgery. Post operative therapy: 4 cycles G 2000 mg/m2 and nab-P 220 mg/m2 q14 days. Myeloid growth factors were mandated with all cycles. 2 antibody reagents were used to probe for SPARC expressions. For this study, level 3 immunohistochemical (IHC) SPARC staining was considered positive. Results: 123 pts have enrolled with pathologic responses available for 106. 82 pts consented to SPARC testing. Median age 51 (29-72). Median tumor size 4.5 cm. Histology: 81% ductal, 10% lobular, 9% other. 42% ER and PR negative. 55% clinical T3/T4 and 66% lymph node positive at presentation. G3/4 toxicity present in >5% of pts: neutropenia 16% (febrile neutropenia 1 pt), thrombocytopenia 9% with arthralgias 11%, fatigue 10%, and infection 7%. 20 pts did not complete study treatment for the following reasons: disease progression 7, toxicity 3, pt/MD request 5, and other 5. pCR was noted in 23 pts (22%) with PRs in 76 pts (71%), and 6 SD. SPARC IHC staining was available for 76 tumors. SPARC level 3 IHC staining was noted in 65 tumors (86%); 65% were associated with a PR or pCR. Median PFS was 23 months and overall survival at 24 months is 77%. Pts who relapsed ≤16 months from diagnosis were more likely to be triple negative (p = 0.04), or ER negative (p = 0.001), or PR negative (p = 0.0006). Conclusions: Neoadjuvant dose dense GEA is active and better tolerated than other gemcitabine/anthracycline/taxane combinations. The pCR rate of 22% compares favorably with other comparable neoadjuvant regimens albeit with minimal toxicity. Pts with early relapse defined as ≤16 months from diagnosis were more likely to demonstrate a triple negative phenotype or demonstrate estrogen or progesterone receptor negativity. SPARC tumor correlatives with progression free and overall survival are on ongoing and will be presented.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5116.

Mechanisms of nab-paclitaxel and bevacizumab cooperation in inhibition of breast tumor growth and metastasis

Abstract #1032

Background: Nab-paclitaxel, also known as Abraxane®, is paclitaxel formulated in nanoparticles that consist of human albumin encapsulating the hydrophobic drug moiety. This drug has shown numerous advantages including linear pharmacokinetics, significantly higher tumor retention, and increased maximal-tolerated dose due to reduced toxicity. We previously showed that combination of Abraxane and anti-VEGF-A antibody, bevacizumab, is significantly more efficacious in suppression of breast tumor xenografts and metastasis as compared to treatments with each of these drugs alone. We hypothesized that the mechanism underlying the therapeutic success of the combined therapy might include bevacizumab-dependent abrogation of the stress response elicited by paclitaxel in the tumor cells surviving chemotherapy.
 Materials and Methods: Cultured MDA-MB-231 cells were treated with 0, 2.5, 5, 10, and 30 nM of Abraxane followed by detection of angiogenic (VEGF-A), prosurvival (p42 & p44 kinase, bcl-2) and inflammatory (IL-6, IL-8, and TNF-α) proteins using Western blotting and ELISA. MDA-MB-231 tumors were extracted from mice upon cessation of intravenous (IV) Abraxane therapy (10 to 30 mg/kg, qdx5) followed by Western blot and immunohistochemical analyses.
 Results: In vitro, Abraxane treatment increased expression of VEGF-A, p42/44 kinase, bcl-2 as well as total and phosphorylated p65 subunit of NF-κB. Treated cells secreted 25- to 30-fold higher concentrations of inflammatory cytokines IL-6, IL-8, and TNF-α into conditioned media as compared with untreated control cells. Likewise, significant increases in bcl-2 and inflammatory cytokines were observed in tumors extracted immediately after paclitaxel therapy in vivo as confirmed by both Western blotting and immunohistochemical analyses.
 Discussion: These findings suggest that paclitaxel elicits VEGF-A dependent prosurvival and proinflammatory stress responses in tumor cells surviving the cytotoxic therapy. Activation of these pathways suggests that concurrent therapy with VEGF-A neutralizing antibody might significantly improve the efficacy of paclitaxel-based therapies by counteracting the stress responses in the therapy-spared tumor cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1032.