A phase I study of obatoclax mesylate, a Bcl-2 antagonist, plus topotecan in solid tumor malignancies

Cancer Chemother Pharmacol. 2010 Nov;66(6):1079-85. doi: 10.1007/s00280-010-1265-5. Epub 2010 Feb 18.


Purpose: To establish the safety, maximum tolerated dose (MTD), recommended phase II dose, and preliminary antitumor activity of obatoclax mesylate (GX15-070MS), a Bcl-2 antagonist, in combination with topotecan in patients with solid tumor malignancies.

Patients and methods: Patients with solid tumor malignancies for whom topotecan was an appropriate treatment were administered obatoclax mesylate and topotecan on a 3-week cycle in a pre-defined, standard 3 + 3 dose escalation scheme. The starting dose for obatoclax mesylate was 14 mg/m(2) by 3-h intravenous (IV) infusion. Topotecan 1.25 mg/m(2) was given concurrently as an IV infusion on days 1-5 of each cycle.

Results: Fourteen patients received 40 cycles of obatoclax mesylate at the following doses: 14 mg/m(2) on day 1, 14 mg/m(2) on days 1 and 3, and 20 mg/m(2) on day 1. The most common toxicities related to obatoclax were neurologic, including ataxia, mood alterations, somnolence, and cognitive dysfunction. The majority of these were grades 1 and 2 (88%). Two of five patients experienced dose-limiting grade 3 neurologic toxicity at a dose of 20 mg/m(2); no patients experienced grade 4 neurologic toxicities, and no other patients experienced grade 3 neurologic toxicity. Of the patients who experienced grade 3 neurologic events, one later developed febrile neutropenia, which was also a dose-limiting toxicity (DLT). After an additional three patients were treated without DLT at the previously tolerated dose of 14 mg/m(2) on day 1, the level was escalated to 14 mg/m(2) on days 1 and 3. Three patients were treated at this dose and, with none experiencing a DLT, 14 mg/m(2) on days 1 and 3 was defined as the recommended phase II dose. Two patients with small-cell lung cancer (SCLC) achieved partial responses and four patients had stable disease. Median time to progression (TTP) was 12 weeks.

Conclusion: Obatoclax mesylate administered at 14 mg/m(2) IV on days 1 and 3 is safe and well tolerated when given in combination with topotecan 1.25 mg/m(2) IV on days 1-5 of an every 3-week cycle. A phase II trial to assess the efficacy of this combination for patients with relapsed SCLC is currently accruing patients.

Publication types

  • Clinical Trial, Phase I
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Apoptosis / drug effects*
  • Carcinoma, Small Cell / drug therapy*
  • Carcinoma, Small Cell / metabolism
  • Carcinoma, Small Cell / pathology
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Female
  • Humans
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Male
  • Maximum Tolerated Dose
  • Mesylates / administration & dosage
  • Middle Aged
  • Patient Selection
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors*
  • Pyrroles / administration & dosage*
  • Pyrroles / adverse effects
  • Recurrence
  • Topotecan / administration & dosage


  • Mesylates
  • Proto-Oncogene Proteins c-bcl-2
  • Pyrroles
  • Topotecan
  • obatoclax