A Phase I, Open-Labeled, Single-Arm, Dose Escalation, Clinical and Pharmacology Study of Dichloroacetate (DCA) in Patients With Recurrent and/or Metastatic Solid Tumours
As cancer cells have a hyperpolarized mitochondrial membrane and deficiency in Kv channel
expression, it was postulated that the reversal of this observation may increase apoptosis
and inhibit tumor growth. Bonnet and colleagues reported that the administration of DCA led
to the switch from glycolysis to oxidative phosphorylation in the Krebs Cycle through
inhibition of PDHK. This was associated with an increase in the production of reactive
oxygen species and a decrease in hyperpolarization of the inner mitochondrial membrane,
leading to efflux of proapoptotic proteins and apoptosis as measured by increased in
TUNEL-positive cells. In addition, DCA also decreased the expression of survivin, an
anti-apoptotic protein. DCA upregulated the expression of Kv channels in cancer cells,
leading to efflux of potassium ions and further increased the proapoptotic effect of DCA.
Such change in energy metabolism and apoptosis was not observed in normal cells. DCA was
also shown to inhibit tumor growth both in vitro and in vivo. Thus, inhibition of PDHK by
DCA represents a novel anti-cancer therapy target with reasonable toxicities to normal
tissue. It is therefore of interest to study DCA in refractory cancer patients.
Although the bioavailability was only 50-60% in normal subjects treated with 2.5
microgram/kg of DCA , in a study using clinically relevant dose of DCA at 50 mg/kg, the
bioavailability was 100% in health volunteers. DCA administered at 50 mg/kg/day can
achieve plasma concentrations above those require for inhibition of PHDK, the target enzyme
for at least 24 hours, without exceeding the concentration for maximal lactate lowering.
There was a high incidence of peripheral neuropathy in adults with MELAS after
administration of DCA at 50 mg/kg/day for 6 months, but peripheral neuropathy is part of the
MELAS syndrome, and many adult patients with MELAS develop diabetes mellitus, which commonly
presents with peripheral neuropathy. In the contrary, no peripheral neuropathy was observed
in children with congenital acidosis after prolonged treatment with DCA at 50 mg/kg/day up
to 2 years. Therefore, with exclusion of patients with any grade 2 or higher peripheral
neuropathy and with careful monitoring of peripheral neuropathy using monofilaments, the
likelihood of developing severe peripheral neuropathy in adult cancer patients should be
minimized. Given the presence of significant neuropathy in adult patients with MELAS after
treatment with DCA at 25 mg/kg/day, it is judged to be safe and reasonable to establish the
starting dose at 12.5 mg/kg/day in adult cancer patients.
Allocation: Non-Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
To assess safety and tolerability of oral DCA
Peter Venner, M.D.
Alberta Health Services
Canada: Ethics Review Committee