Pimitespib (12.0 mg/kg, p.o., 14 days) shows antitumor activity without inducing eye injury in rats. Pimitespib is distributed less in retina than in plasma in rats; consequently, Pimitespib does not produce any detectable photoreceptor injury. Pimitespib triggers enhanced in vivo anti-MM activities, both alone and in combination with PS-341 (BTZ), with a favorable safety profile. Mice treated with Pimitespib (10 mg/kg and 15 mg/kg, orally, 38 days), BTZ, or Pimitespib plus BTZ show significantly enhance growth inhibition versus the vehicle control group. Median overall survival of treated animals (Pimitespib, orally, 10 mg/kg=33 days, 15 mg/kg=37 days, BTZ=36 days, and the combination=56.5 days) is significantly longer than vehicle control.
The favorable pharmacokinetic profile of Pimitespib is reflected in its dose-dependent antitumor activity; the T/C (tumor volume of Pimitespib-treated mice vs. vehicle-treated mice) is 47%, 21%, and 9% for doses of 3.6 mg/kg, 7.1 mg/kg, and 14.0 mg/kg, respectively. Pimitespib is orally absorbed and has a bioavailability of almost 100% in mice, and 69.0% in rats. Pimitespib has moderate terminal elimination half-life (t1/2=8.2 h, 2.5 h, 4.4 h and 2.2 h for mouse (3.6 mg/kg, p.o.), mouse (7.1 mg/kg, p.o.), mouse (14.0 mg/kg, p.o.), rat (4 mg/kg, p.o.)). Pimitespib is more rapidly eliminated from retina (t1/2=3.4 hours) than the other HSP90 inhibitors (t1/2=7.1-19.1 hours).
Animal Model: |
Male F344 nude rats (6 weeks old) with established NCI-H1975 xenografts (6 weeks old) |
Dosage: |
12.0 mg/kg |
Administration: |
Oral administration; daily; two weeks |
Result: |
Led to tumor shrinkage. Showed antitumor activity without inducing eye injury in rats and did not cause ocular toxicity at the effective dose in the NCI-H1975 rat xenograft model. |
Animal Model: |
CB17 SCID mice (48-54 days old) with murine xenograft model
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Dosage: |
10 and 15 mg/kg |
Administration: |
Oral administration; 5 days a week; for 28 days |
Result: |
Enhanced significantly growth inhibition versus the vehicle control group. The delay in tumor growth was greater in the combination-treated group compared with either monotherapy cohort.
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Animal Model: |
Mice, Rats, and Dogs
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Dosage: |
3.0 mg/kg for dogs, 4.0 mg/kg for rats, 3.6, 7.1 and 14.0 mg/kg for mice |
Administration: |
Oral administration; daily; 20 days |
Result: |
Absorbed orally and had a bioavailability of almost 100% in mice, 69.0% in rats, and 73.9% in dogs without special formulation.
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