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J.S. De Bono
MO09 - Mesothelioma I (ID 120)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Presentations: 1
- Moderators:K. Suzuki, S.G. Armato III
- Coordinates: 10/28/2013, 16:15 - 17:45, Bayside 204 A+B, Level 2
MO09.01 - Evaluation of tolerability and anti-tumor activity of GDC-0980, an oral PI3K/mTOR inhibitor, administered to patients with advanced malignant pleural mesothelioma (MPM) (ID 1712)
16:15 - 17:45 | Author(s): J.S. De Bono
The PI3K-AKT-mTOR signaling pathway is dysregulated in a wide variety of cancers. Pathway activation in mesothelioma may occur through diverse cellular mechanisms, including activation of receptor tyrosine kinases that signal through Ras and PI3K/Akt/mTOR, and loss of PTEN expression. GDC-0980 is a potent and selective oral dual inhibitor of class I PI3K and mTOR kinases that has demonstrated broad activity in various xenograft cancer models.
A phase I dose-escalation study was conducted in 2 Stages: Stage 1 evaluated oral, daily (QD) doses of 2-70 mg GDC-0980 given 21/28 or 28/28 days in a 3+3 dose escalation design. Stage 2 evaluated disease specific cohorts at the recommended phase 2 dose (RP2D), including a MPM cohort at 30 mg GDC-0980 QD 28/28 days. Safety and tolerability of GDC-0980 was assessed as well as pharmacokinetics (PK) and pharmacodynamics (PD) assessment of PI3K pathway inhibition by FDG-PET. Anti-tumor activity was assessed by modified RECIST; CT scans were centrally reviewed retrospectively by a radiologist with MPM expertise. Archival tumor tissue was evaluated for PIK3CA mutation by allele specific PCR or Sanger sequencing and PTEN expression was assessed by immunohistochemistry.
33 MPM patients were enrolled: 6 in Stage 1 at 8-70 mg and 27 in Stage 2 at 30mg GDC-0980. Safety and tolerability of GDC-0980 in Stage 1 was similar in MPM compared to other solid tumor patients, with the exception of a Grade 5 pneumonitis that occurred in a MPM patient at 40 mg GDC-0980 QD. Based on Stage 1 tolerability data, a RP2D of 30 mg QD was evaluated in Stage 2 for MPM patients. The most frequent Grade ≥3 drug-related adverse events (AEs) at 30 mg GDC-0980 were rash (19%), with one patient (4%) having to discontinue GDC-0980. Other AEs were fatigue (15%), and hyperglycemia, diarrhea, and colitis (7% each). Reversible Grade 2 pneumonitis was reported for 2 patients (7%). Population PK analysis was used to assess the behavior of GDC‑0980 in MPM patients. Additionally, PK/PD relationships will be discussed for efficacy and safety, including exposure‑response, where appropriate. Archival tissue was analyzed for 29 MPM patients. Two samples had PIK3CA mutations (R88Q and E545G) and one sample showed loss of PTEN expression. PI3K pathway inhibition by FDG-PET responses was observed in 8 of 24 MPM patients with available scans. Anti-tumor activity was observed in both stages. Two patients achieved a partial response (PR) in Stage 1, one patient at 50 mg and one patient with the PIK3CA mutation R88Q at 8 mg GDC-0980. Two PRs were observed at the RP2D of 30 mg in Stage 2. Eleven (41%) MPM patients at the RP2D remained on study for >6 months, and 2 (7%) patients remained on study >12 months.
GDC-0980 was generally well tolerated in MPM patients at the RP2D. Anti-tumor activity, evidenced by tumor regression and prolonged disease control, has been observed. PIK3CA mutations and PTEN loss were uncommon.
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