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.

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A phase II trial of IPI-504 (retaspimycin hydrochloride), a novel Hsp90 inhibitor, in patients with relapsed and/or refractory stage IIIb or stage IV non-small cell lung cancer (NSCLC) stratified by EGFR mutation status

8073

Background: IPI-504 (retaspimycin hydrochloride) is a potent, water-soluble heat shock protein 90 (Hsp90) inhibitor. IPI-504 causes the degradation of mutated epidermal growth factor receptor (mtEGFR) kinase and cMET in NSCLC cell lines. IPI-504 also significantly reduces tumor growth in murine xenograft models, including tumors resistant to tyrosine kinase inhibitors (TKIs). Methods: This phase II trial is investigating the safety and antitumor activity of intravenous (IV) 400 mg/m2 IPI-504 given twice weekly for 2 out of 3 weeks. Eligible patients (pts) had stage IIIb (w/ malignant effusion) or stage IV NSCLC that progressed after TKI treatment. EGFR mutation analysis was performed on all pts. Two cohorts (n=10 each) were initially enrolled and stratified by EGFR status (mtEGFR or wtEGFR). Planned cohort expansion to 29 pts occurred if ≥ 1 pt from that cohort had a best response of stable disease (SD) ≥12 wks or partial response (PR). Pts were evaluated for safety and RECIST response every 6 weeks. Central, independent radiology review was performed for all imaging studies. Results: 43 pts have been enrolled: 10 mtEGFR, 17 wtEGFR, 12 pending analysis, and 4 EGFR-failed samples. 19 pts are currently on study. Median age is 62 yrs (range 31–77). Median no. of prior therapies is 3. Common related adverse events are fatigue, nausea, and diarrhea. Anti-tumor activity has been observed, see table. Both cohorts have been expanded. Conclusions: IPI-504 monotherapy has been well tolerated, with evidence of anti-tumor activity, particularly and unexpectedly in the wtEGFR cohort. These data suggest that IPI-504 may have antitumor activity in heavily pretreated pts with advanced NSCLC. Further evaluation continues in the expansion phase of the trial.

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Inhibition of the Heat Shock Protein 90 (Hsp90) chaperone with the novel agent IPI-504 to overcome resistance to tyrosine kinase inhibitors (TKIs) in metastatic GIST: Updated results of a phase I trial

10024

Background: Prior work from our team demonstrates that inhibition of the Hsp90 chaperone protein results in preferential destruction of the mutated KIT kinase in human GIST cell lines regardless of TKI-resistance mutations. To translate this into clinical application, we are conducting a phase I trial of IPI-504, a novel Hsp90 inhibitor, for patients (pts) with metastatic TKI-resistant GIST. Methods: Pts with metastatic TKI-resistant GIST were eligible to enter and receive IPI-504, IV in 250 cc of normal saline over 30 mins, on days 1, 4, 8 and 11 of a 21 day cycle. Serial monitoring with 18FDG-PET/CT imaging at baseline, day 11, and day 21, as well as PK profiling of IPI- 504 and its major active metabolites (17-AAG and 17-AG), were performed on all pts. Results: 21 pts with progressive GIST after both prior imatinib and sunitinib have been entered at 5 dose levels (90 mg/m2 IPI-504 [n=6], 150 [3], 225 [3], 300 [3], 400 [6]); 18 are now evaluable. The maximal tolerated dose has not been reached, and enrollment is ongoing. AEs possibly related to IPI-504 include Grade 1–2 elevation of alkaline phosphatase, fatigue, and headache; one DLT was observed in the 1st and 5th dose levels. PET demonstrated decreases in tumor FDG avidity in 1/6 pts, 1/3, 3/3, 1/3, and 2/3 at the respective dose levels in this schedule (3 patients were inevaluable by PET). Reactivation of tumor FDG uptake by PET was seen during the planned 10-day breaks in IPI-504 administration with reinduction of decreased tumor FDG avidity upon re-treatment with IPI-504. Although no RECIST-defined “anatomic responses” were noted, stable disease has allowed 7 pts to continue on study treatment for ≥ 4 cycles. Conclusions: Targeting Hsp90 is a novel therapeutic strategy in TKI-resistant GIST. IPI-504 has been well-tolerated overall, and the activity seen with decreased FDG avidity of GIST lesions, as well as the induction of SD in pts with documented prior progression, is promising with this non-TKI agent. Reactivation of PET signal in lesions during breaks in IPI-504 dosing is similar to flares with TKI discontinuation. To address this, a new schedule of continuous BIW dosing of IPI-504 has been added to optimize drug exposure.

No significant financial relationships to disclose.

Mutations in human TBX5 [corrected] cause limb and cardiac malformation in Holt-Oram syndrome

Holt-Oram syndrome is characterized by upper limb malformations and cardiac septation defects. Here, we demonstrate that mutations in the human TBX5 gene underlie this disorder. TBX5 was cloned from the disease locus on human chromosome 12q24.1 and identified as a member of the T-box transcription factor family. A nonsense mutation in TBX5 causes Holt-Oram syndrome in affected members of one family; a TBX5 missense mutation was identified in affected members of another. We conclude that TBX5 is critical for limb and heart development and suggest that haploinsufficiency of TBX5 causes Holt-Oram syndrome.