A phase I study of dasatinib and weekly paclitaxel for metastatic breast cancer

BACKGROUND

SRC plays an important role in the pathogenesis of metastatic breast cancer (MBC). In preclinical models, paclitaxel and the oral SRC inhibitor dasatinib showed greater antitumor activity than either agent. To determine the maximum tolerated dose of this combination, we conducted a phase I study.

PATIENTS AND METHODS

Patients with MBC; Eastern Cooperative Oncology Group performance status of zero to one; normal hepatic, renal and marrow function were eligible. Paclitaxel 80 mg/m(2) was given 3 weeks of 4. The starting dasatinib dose was 70 mg and was increased, using a standard 3 + 3 dose-escalation scheme.

RESULTS

Fifteen patients enrolled (median age 54 years, range 35-74). No dose-limiting toxic effects (DLTs) occurred at dasatinib doses of 70-120 mg. One DLT (grade 3 fatigue) occurred in the dasatinib 150-mg cohort, which was expanded (six patients) with no further DLTs. However, due to cumulative toxic effects (rash, fatigue, diarrhea), the recommended phase II dose is dasatinib 120 mg. Of 13 assessable patients, a partial response was seen in 4 patients (31%), including 2 patients previously treated with taxanes; all received ≥120 mg dasatinib. An additional five patients (29%) had stable disease.

CONCLUSION

In combination with weekly paclitaxel, the recommended phase II dose of dasatinib is 120 mg daily and preliminary activity has been seen in patients with MBC.

Abstract P6-12-09: A Phase I-II Trial of Dasatinib (D) in Combination with Weekly (w) Paclitaxel (P) for Patients (Pts) with Metastatic Breast Carcinoma (MBC)

Background: Inhibition of SRC is a novel approach for MBC. D is an inhibitor of multiple tyrosine kinases, including the SRC family. Pre-clinical data show D inhibits multiple breast cancer cell lines, including those of “basal-like” subtype. In preclinical models D + P had superior antitumor activity to either agent alone. We designed this phase I-II study to translate this observation.

Methods: For phase I: pts with MBC, ECOG PS 0-1, normal hepatic, renal, marrow function were eligible. Pts with pleural/pericardial effusions were excluded. For phase II: pts had measurable, HER2-negative MBC, ≥2 prior rx for MBC. Prior taxanes, stable brain metastases and baseline neuropathy grade ≥1 were allowed. Cycle (C) consisted of wP 80 mg/m2 IV 3/4 weeks + D 70mg orally daily; escalating to 100 mg, 120 mg and 150 mg in cohorts of 3pts. Toxicity was assessed by CTCAE v3.0, response by RECIST.

Results: 17 pts enrolled (15 phase I; 2 phase II); median age 54 (range 35-74), median PS=1 (range 0-1). 12 (71%) pts rcvd prior adjuvant chemoRx. Pts rcvd a median of 3 prior rx for MBC (range 0-12). Pts rcvd median of 2 C of D + P (range 1-14). One DLT occurred at 150mg (G3 fatigue); this cohort was expanded with no further DLTs. However 3 pts on this dose level withdrew;1 pt delayed hypersensitivity rash (grade 1), 1 pt febrile neutropenia (grade 3), 1 pt paclitaxel pneumonitis (grade 3). Therefore the phase II dose is D 120mg. Overall the most common toxicities have been hematologic and low G (table). 13 pts are assessable for response; 4 patients (31%) had a PR, including 3 patients previously treated with taxanes. 5 pts (29%) had stable disease.

Toxicities > Grade 1

Conclusion: Treatment with wP and D is feasible in pts with MBC. In the phase I study, 1 DLT occurred at D 150mg but due to cumulative toxicities the recommended dose for the ongoing phase II study is 120mg. Preliminary evidence of activity has been seen in taxane-pretreated pts at the phase II dose. Identification of biomarkers to select appropriate pts for this therapeutic approach is the subject of ongoing correlative studies.

Safety of a novel capecitabine dosing schedule when combined with lapatinib in patients with HER2-positive metastatic breast cancer refractory to trastuzumab

1131

Background: Capecitabine (C) is active in breast cancer and is usually dosed for 14 days (d) followed by a 7d rest (14 - 7). We described a mathematical method which predicts the optimal schedule for C to be 7d followed by a 7d rest (7 - 7) (Norton et al, Amer Assn Can Res. 2005). The MTD of C(7 - 7) is 2,000mg BID (Traina et al, J Clin Oncol. April 2008). Lapatinib (L) improves time to progression when added to C(14 - 7) in patients (pts) with HER-2-positive (+) metastatic breast cancer (MBC) that progressed after trastuzumab (T). To optimize this effective combination, we are testing C(7 - 7) + L in a phase II trial. Methods: Eligible pts have measurable, HER-2(+) MBC that has progressed after T. HER-2(+)=IHC 3+ or FISH>2. Pts have normal LVEF by MUGA, ECOG performance status (PS) <2 and normal organ function. <3 prior chemotherapy (CRx) regimens are permitted. Prior fluoropyrimidine is excluded. Therapy (tx) consists of C (2,000 mg BID, 7 - 7) and L (1,250 mg, daily). Cycle length = 4 wk. Pts are evaluated for toxicity q4 weeks (wk), for response q12wk; LVEF by MUGA q12wk. Primary endpoint: response rate (RR). Secondary endpoints: toxicity, stable disease >6 months, PFS. Using a Simon optimal 2-stage design, with alpha = 10%, power = 90% to discriminate between RR 10% and 25%, 21 pts will be accrued to the first stage. If >2 pts respond, 29 additional pts will be enrolled. If >7/ 40 pts respond, then C(7 - 7) + L will be considered worthy of further study. Results: As of January 5, 2008, 6 pts are enrolled and evaluable. Median (med) age 64 yrs (42–71), med ECOG PS 1 (0–1), ER/PR(+) 3, HER-2(+) 6, sites of MBC: bone (2), viscera (4), soft tissue (5). Med baseline LVEF 62% (51–68%). Prior tx: Adjuvant: CRx (5), hormone tx (3), T (3); MBC: CRx (2), hormone tx (1), T (3). After a med of 3 cycles (1–4), there were no grade 3, 4, or 5 events. Tx-related toxicity is: Gr 2 fatigue (1); Gr 1 AST (4), diarrhea (3), ALT (2), vomiting (1), hand-foot (1), fatigue (1). No withdrawls due to reduced LVEF. Two pts evaluable for response: PR = 1, SD<6 mo = 1. Conclusions: Capecitabine (7 - 7) + lapatinib appears well tolerated compared to C(14 - 7)+L (Geyer et al). Additional safety and efficacy data is anticipated prior to this meeting.

[Table: see text]

Dose-dense (DD) doxorubicin and cyclophosphamide (AC) followed by weekly paclitaxel (P) with trastuzumab (T) and lapatinib (L) in HER2/neu-positive breast cancer is not feasible due to excessive diarrhea: updated results

Abstract #2108

Background: DD q 2 weekly (w) AC → P + T x 1 year (y) has an acceptable safely profile w/ congestive heart failure (CHF) rate of 1/70 pts (Dang, JCO 2008). Lapatinib (L) is effective in HER2 (+) BC. We conducted a pilot study of dd AC → w P + T + L to determine its feasibility and cardiac safety.&#x2028; Methods: Enrolled pts had HER2 (+) BC; LVEF &gt; 50%. Rx consisted of AC at 60/600 mg/m2 x 4 q 2 w (w/ pegfilgrastim 6 mg day 2) → P at 80 mg/m2 x 12 q w + T x 1 y; L (1000 mg daily beginning w/ P + T and continued x 1 y). MUGA is obtained at baseline and at months (mo) 2, 6, 9, and 18. Rx is considered feasible if 1) &gt; 80% pts can complete the PTL phase without a dose delay or reduction and 2) the cardiac event rate (CHF or cardiac death) is &lt; 4%. Pts can remain on-Rx w/ one dose reduction of L (1000 mg → 750 mg) for a G 3 event or &lt; G 3 toxicity (unacceptable).&#x2028; Results: From March 2007 to April 2008, we enrolled 95 pts. Median (med) age was 45 years (range, 28-73). At a med follow-up of 7 months, 90 are evaluable. Of the 90 pts, 34 (37%) withdrew from study during the PTL phase; 29 for a 2nd event of G 3 or unacceptable &lt; G 3 toxicities (15 G 3 diarrhea, 4 G 1/2 diarrhea, 1 G 3 rash, 2 G 2 rash, 1 G 3 dyspnea and also had G 3 diarrhea, 1 G 3 ↑QTc also had G 3 diarrhea, 1 G 3 ↑ALT also had G 3 diarrhea, 1 G 3 paronychia, 1 G 3 pneumonitis, 1 asymptomatic LVEF ↓, 1 myocarditis) and 5 for other reasons (2 personal reason, 1 PCP pneumonia, 1 progression, 1 P hypersensitivity). Overall, 25/90 (27%) pts had G 3 diarrhea and 31/90 (34%) pts required a dose reduction of lapatinib. Med LVEF at baseline is 67% (N=95), at mo 2 is 68% (N=90), at mo 6 is 65% (N=53), and mo 9 is 65% (N=28). To date there are no patient drop-outs due to significant LVEF declines after dd AC; one patient dropped during PTL out due to an asymptomatic LVEF decline.&#x2028; Discussion: L at 1000 mg/day is not feasible combined w/ weekly P and T by protocol stipulation (&gt; 20% pts required L dose reduction) primarily due to excessive G 3 diarrhea. These results have led to the modification of Design 2 (Arm D) of ALTTO. We will report updated results.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2108.

A phase II study of XL999 in patients (pts) with NSCLC

18112

Background: XL999 is a potent spectrum-selective inhibitor of receptor tyrosine kinases including VEGFR2/KDR, FGFR1/3, PDGFR-β, FLT3, RET, KIT, & SRC. A Ph 1 clinical study in pts w/advanced malignancies evaluating weight-based (0.2 - 6.4 mg/kg) & fixed dose (200 mg & 160 mg) XL999 administered by 4hr IV infusion on a wkly or every other wk schedule has shown preliminary evidence of anti- tumor activity (3 PRs & 10 pts w/SD lasting 3–26+ months). The safety profile was characterized by hypertension & cardiovascular changes including EKG, LVEF decrease &/or cardiac enzyme elevation following 1st dose administration. DLTs were cardiac failure & transaminase elevation. A dose of 2.4 mg/kg/wk was selected for phase II evaluation. Methods: The 1 objectives of this phase II study are to determine the RR & to further evaluate the safety & tolerability of XL999. Adult pts w/NSCLC (stage IIIB with malignant effusion, stage IV, or recurrent) & previously treated with no more than 2 prior systemic cytotoxic chemotherapy regimens, including a platinum-or taxane-containing regimen, & no more than one prior target agent targeting VEGF or EGFR, are eligible. Additional inclusion criteria include ECOG PS 0–1 & absence of known brain metastases. Pts with LVEF<50% or below lower limits of normal or with significant cardiovascular abnormalities are excluded. Tumor response is assessed every 8 wks by RECIST criteria. XL999 is administered wkly at 2.4 mg/kg as a 4hr IV infusion. Results: Nine pts received XL999. Three pts remain on study drug. One pt has a confirmed PR with complete resolution of a 2cm lung nodule. Another has a total reduction of 23% in multiple hepatic lesions (by RECIST). A third pt continues with SD for 3.5 months. Six pts with PD are discontinued. AEs reported in at least 2 pts were grade 1 diarrhea, fatigue, anorexia, & dizziness. Grade 3 AEs included 1 report each of N/V. No Grade 4 or 5 AEs or serious cardiac AEs have been reported. Conclusions: Wkly IV dose at 2.4 mg/kg appears generally well-tolerated & shows preliminary evidence of anti-tumor activity in advanced NSCLC pts refractory to multiple prior anti-cancer therapies.

No significant financial relationships to disclose.

Tolerability and hematologic improvement assessed using three alternative dosing schedules of azacitidine in patients with myelodysplastic syndromes

7083

Background: At a dosing schedule of 75 mg/m2/day SC for 7 days every 4 weeks, azacitidine is an effective and safe treatment (Tx) for patients (pts) with myelodysplastic syndromes (MDS) (JCO 2002; 20:2429). An alternative dosing schedule that eliminates the need for weekend dosing would be more convenient to pts and clinicians. Methods: In this phase II, multicenter, open-label trial, pts with MDS were randomized to 1 of 3 regimens that were repeated every 4 weeks: AZA 5–2-2 (75 mg/m2/day × 5 days, followed by 2 days no Tx, followed by 75 mg/m2/day × 2 days), AZA 5–2-5 (50 mg/m2/day × 5 days, followed by 2 days no Tx, followed by 50 mg/m2/day × 5 days) or AZA 5 (75 mg/m2/day × 5 days). To determine if response/improvement according to International Working Group criteria (Blood 2000; 96:3671) can be maintained after 6 cycles, the study was amended to include a 12-month maintenance comparing AZA 5 every 4 weeks with AZA 5 every 6 weeks. Results: As of Nov. 30, 2006, 138 pts have been randomized to AZA 5–2-2 (n=46), AZA 5–2-5 (n=47) and AZA 5 (n=45). Most pts are RA (43%) or RAEB (30%), based on FAB classification. Of 104 pts who have received =2 cycles of Tx, hematologic improvement (major or minor in at least 1 cell line) occurred in 63% (65) of the patients ( Table ). Of these pts, 14% had a bi-lineage (AZA 5–2-2: 11%, AZA 5–2-5: 10%, AZA 5: 22%) and 6% had a tri-lineage AZA 5–2-2: 6%, AZA 5–2-5: 7%, AZA 5: 5%) response (based on any improvement). Ongoing pts in the study include AZA 5–2-2: 41% (19/46), AZA 5–2-5: 47% (22/47), and AZA 5: 58% (26/45). No treatment-related mortality has been reported. Most Tx-related grade 3 or 4 events were hematological (AZA 5–2-2: 39%, AZA 5–2-5: 24%, AZA 5: 16%). Updated data, including several pts who have completed at least 6 cycles maintenance, will be available at the time of the meeting. Conclusions: These data indicate that the 3 alternative azacitidine dosing schedules are safe, effective, and similar in efficacy with the FDA-approved regimen.

[Table: see text] [Table: see text]

A phase I study of trastuzumab-MCC-DM1 (T-DM1), a first-in-class HER2 antibody-drug conjugate (ADC), in patients (pts) with HER2+ metastatic breast cancer (BC)

1042

Background: ADCs utilize tumor-specific and/or over-expressed surface antigens that undergo internalization to deliver highly potent anti-tumor agents via linkage to antigen-specific monoclonal antibodies (MoAbs). T-DM1 contains the humanized anti-HER2 MoAb trastuzumab (T) previously demonstrated to prolong survival in HER2+ BC to which a highly potent antimicrotubule drug (DM1) derived from maytansine has been chemically linked. Maytansine has been studied as a free drug with responses noted in breast and lung cancer pts; principal adverse events (AEs) were nausea, vomiting, diarrhea, and neuropathy. The MCC linker employed in T-DM1 provides a stable bond between T and DM1 that is designed to prolong exposure and reduce the toxicity of T-DM1 while maintaining activity; T-DM1 is the first ADC with an MCC linker in clinical trials. T-DM1 has activity in T-resistant HER2+ BC xenografts; its principal preclinical toxicities were reversible transaminase elevations, reversible decreases in platelets, and neuropathy. Methods: This ongoing first-in-human phase I study is evaluating the safety and pharmacokinetics (PK) of T-DM1 given IV q3 weeks to pts with HER2+ metastatic BC who have progressed on a T-containing regimen. Results: Seven pts (median age 58 (range 47–70); all PS 0–1; median number prior chemo regimens 6 (range 5–11)) have received 24 doses of T-DM1 at 5 dose levels (0.3–4.8 mg/kg). Related grade (gr) 1–2 AEs include elevations in hepatic transaminases (2 pts), fatigue (2 pts), anemia (1 pt), and thrombocytopenia (TCP, 1 pt). Related gr 3–4 AEs have been limited to rapidly reversible gr 4 TCP at 4.8 mg/kg (1 pt). There has been no cardiac toxicity. Consistent with preclinical modeling, dose dependent decrease in clearance was observed for T-DM1 across dose levels. One pt at 2.4 mg/kg has maintained an ongoing partial response for 6 cycles. Conclusions: At these initial doses, gr =2 AEs related to T-DM1 have been infrequent and manageable; gr 4 (dose-limiting) rapidly reversible TCP was seen at 4.8 mg/kg. T-DM1 PK is consistent with q3-week dosing. Objective tumor response has been observed. Enrollment is ongoing to determine the maximum tolerated dose of q3-week T-DM1.

No significant financial relationships to disclose.

Phase I trial of alvespimycin (KOS-1022; 17-DMAG) and trastuzumab (T)

1115

Background: Alvespimycin (A) inhibits the activity of Hsp90, resulting in degradation of client proteins, such as the HER2 receptor. In vivo, Hsp90 inhibition induces rapid degradation of HER2 with loss of pAKT, cyclin D2 and tumor growth inhibition. Methods: Pts receive standard weekly doses of T followed by A in escalating doses via IV doses over 1 hr. Define the recommended dose (RP2D), toxicity and signs of activity of T+A in pts with solid tumors. PK: assessed after the 1st and 4th infusion. PBLs: purified to investigate changes in intracellular signaling proteins by immunoblot. The RP2D will produce DLT in no more than 1/6 evaluable pts. Results: 21 pts enrolled in 3 cohorts (60, 80 and 100 mg/m2). Median age 53 yrs, range 31–75; median KPS 90; prior regimens not including hormonal therapy: median 6, range 1–13; prior T-regimens for MBC pts: median 3, range 0–9. Diagnoses: HER2+ MBC (n=18), ovarian (n=3). DLT was observed at the highest dose, consisting of 1 pt with hypoxia and ↓LVEF; an additional pt at this dose had Grade 3 ↑AST, however ↑hepatic metastases and ascites were observed. Drug-related toxicity: diarrhea (60%), fatigue, headache (both 45%), nausea, arthralgias (both 40%), dry eye and pain in extremity (both 25%); all Grade 1–2 severity except 1 episode of Gr3 fatigue and Gr3 diarrhea. PK (n=18): t½ 17.7 hr (32%CV); Clearance 18.1 L/hr (46%CV); Vz 438L (42%CV); no change upon weekly dosing. AUCinf/Cmax (100 mg/m2): 14268 ng*hr/mL (60%CV) and 2233 ng/mL (23.5%CV). HER2+ MBC activity: 1 pt (13 prior regimens; 3x T and 1x lapatanib) with evaluable disease showed near complete resolution of lung metastases by CT/PET with significant improvement in dyspnea; 3 pts with HER2+ MBC with SD (4, 5 and 7+ months). Ovarian CA activity: 1 pt (HER2 unknown; 13 prior regimens; 11+ months on-study) with evaluable disease showed near complete resolution of ascites and pleural effusion at end of Cycle 2 with ↓83% CA125. Dose-dependent increase in Hsp70 in PBLs; at 80 and 100 mg/m2, Hsp70 induction was maintained prior to successive weekly doses. Conclusions: Combination of T+A has signs of activity in H-refractory HER2+ MBC and refractory ovarian cancer. Definition of RP2D dose is pending. Toxicity has been manageable.

No significant financial relationships to disclose.

Human lymphatic pumping measured in healthy and lymphoedematous arms by lymphatic congestion lymphoscintigraphy

Axillary surgery for breast cancer partially obstructs lymph outflow from the arm, chronically raising the lymphatic smooth muscle afterload. This may lead to pump failure, as in hypertensive cardiac failure, and could explain features of breast cancer treatment-related lymphoedema (BCRL) such as its delayed onset. A new method was developed to measure human lymphatic contractility non-invasively and test the hypothesis of contractile impairment. 99mTc-human IgG (Tc-HIG), injected into the hand dermis, drained into the arm lymphatic system which was imaged using a gamma-camera. Lymph transit time from hand to axilla, ttransit, was 9.6+/-7.2 min (mean+/-s.d.) (velocity 8.9 cm min(-1)) in seven normal subjects. To assess lymphatic contractility, a sphygmomanometer cuff around the upper arm was inflated to 60 mmHg (Pcuff) before 99mTc-HIG injection and maintained for>>ttransit. When Pcuff exceeded the maximum pressure generated by the lymphatic pump (Ppump), radiolabelled lymph was held up at the distal cuff border. Pcuff was then lowered in 10 mmHg steps until 99mTc-HIG began to flow under the cuff to the axilla, indicating Ppump>or=Pcuff. In 16 normal subjects Ppump was 39+/-14 mmHg. Ppump was 38% lower in 16 women with BCRL, namely 24+/-19 mmHg (P=0.014, Student's unpaired t test), and correlated negatively with the degree of swelling (12-56%). Blood radiolabel accumulation proved an unreliable measure of lymphatic pump function. Lymphatic congestion lymphoscintigraphy thus provided a quantitative measure of human lymphatic contractility without surgical cut-down, and the results supported the hypothesis of lymphatic pump failure in BCRL.

Tranfusion independence assessed using three alternative dosing schedules of azacitidine in patients with myelodysplastic syndromes

6574

Background: The dosing schedule of azacitidine (75 mg/m2/day subcutaneous [SC] × 7 days, every 28 days) decreased transfusion requirements in myelodysplastic syndrome (MDS) patients in a CALGB trial by Silverman et al (JCO 2002;20:2429). Our study assessed effects on transfusion requirements in MDS patients receiving 3 alternative azacitidine dosing regimens not requiring weekend injections. Methods: This phase II, multicenter study enrolled MDS patients with any FAB subtype, life expectancy ≥7 months, and ECOG performance grade of 0–3. RA/RARS patients had to have ≥1 of the following: hemoglobin <110 g/L with transfusion need, platelet counts <100 × 109/L, or ANC <1.5 × 109/L. Patients were randomized to 1 of 3 SC regimens: AZA 5–2-2 (75 mg/m2/day × 5 days, followed by 2 days no treatment, followed by 75 mg/m2/day × 2 days), AZA 5–2-5 (50 mg/m2/day × 5 days, followed by 2 days no treatment, followed by 50 mg/m2/day × 5 days), or a 3rd regimen added later by protocol amendment: AZA 5 (75 mg/m2/day × 5 days). After 6 cycles, patients meeting International Working Group MDS response/improvement criteria (Blood 2000;96: 3671) of ≥ stable disease could continue in study for 12 more cycles. Results: In all, 75 patients (median age, 74.5 years; 61% male) are currently enrolled with 49 evaluable (completed ≥ 2 treatment cycles). To date, 12, 9, and 1 patient(s) have received ≥6 cycles of AZA 5–2-2, AZA 5–2-5, or AZA 5, respectively. RA + RARS, defined by FAB (60%) or WHO (47%), are the most common MDS subtypes. Of 24 patients, RBC transfusion dependent at baseline, 13 (54%) became independent ( Table ). Only 2 patients were platelet transfusion dependent at baseline; both became independent. After a median followup of 24 weeks, median duration of transfusion independence has not been reached. Conclusions: Treatment with azacitidine yields transfusion independence rates of 40%-60%. These preliminary results are similar across the 3 alternative doses and consistent with previous azacitidine data.

[Table: see text]

No significant financial relationships to disclose.

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]

Sustained expression of Mect1-Maml2 is essential for tumor cell growth in salivary gland cancers carrying the t(11;19) translocation

Mucoepidermoid (MEC) salivary gland tumors arise from a t(11;19) rearrangement which generates a fusion oncogene, Mect1-Maml2, that functions to activate CREB-responsive target genes. To determine if sustained expression of Mect1-Maml2 is required for tumor cell growth, we first showed that ectopic expression of Mect1-Maml2 in rat epithelial RK3E cells is tumorigenic in vivo in nude mice and that excised xenografts continue to express the fusion oncogene. We then generated a hairpin RNAi vector that selectively suppressed the fusion peptide and showed that ectopic expression in either parotid or pulmonary MEC tumor cell lines containing the t(11;19) rearrangement resulted in at least 90% colony growth inhibition. In contrast, single nucleotide changes within this RNAi sequence abolished the ability to suppress Mect1-Maml2 protein and abolished all growth inhibition of these MEC tumor lines. In addition, the RNAi-specific vector had no effect on colony growth of non-MEC tumors including a lung tumor or two other salivary gland cell lines that do not express Mect1-Maml2. We also generated a mutant Mect1-Maml2 expression plasmid that carried silent nucleotide changes within the RNAi target sequence and observed that co-transfection of this mutant, but not wild-type Mect1-Maml2, could partially rescue RNAi growth inhibition in the MEC tumor line. The recent detection of acquired fusion oncogenes in epithelial solid tumors has suggested new possibilities for the diagnosis and therapy of these cancers. Our data show that the 'gain-of-function' activity from aberrant Mect1-Maml2 expression is a candidate therapeutic target for this group of malignant salivary gland tumors.