Phase I study of bortezomib and oxaliplatin (BOX) in solid tumors: Improved neurotoxicity (NT) profile with lower bortezomib (B) dose

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Background: B inhibits proteasome function and may be synergistic in causing apoptotic death with platinum agents. We were interested in combining B with OX but concerned with dose limiting (DL) NT based on our prior B phase I study [Hamilton et al., JCO 2005]: therefore this Phase I dose-escalation study (alternating increases of B and OX) focusing on NT was planned. Methods: Patients (pts) with metastatic solid tumors, PS 0–2, platinum or taxane naive, no peripheral neuropathy and adequate organ function, received B (D1, 4, 15, 18) and OX (D1, 15) every 28 days in a dose escalation design (see table ). Baseline and monthly assessments were performed by an independent neurologist. Results: 27 (18 gastrointestinal, 3 melanoma, 3 ovarian, 3 others) were accrued; pt characteristics: 14 male/13 female; median age 55 years (range 35–75); 2 median cycles (range 1–10). NT was not DL because it did not occur within the first cycle. Late and limiting NT was observed in levels 2–5 after 2–9 cycles, but serial neurologic evaluations showed reversible NT. With an amended new dose level to lower B to 1.0 mg/m2 (level 6) to avoid late NT, NT was not observed. Of 22 evaluable pts, there were 3 partial responses (ampullary, GE junction, biliary), 6 stable disease, and 13 disease progression by RECIST criteria. Conclusions: biweekly BOX is tolerable at B 1.0 mg/m2 and OX 85 mg/m2 with no DL NT. Additional observations on late NT are ongoing. This suggests B is a major contributor to NT observed in dose levels 2–5 and may potentiate the effects of OX.

[Table: see text]

[Table: see text]

Nucleus accumbens muscarinic receptors in the control of behavioral depression: antidepressant-like effects of local M1 antagonist in the Porsolt swim test

Systemically administered cholinomimetics or cholinesterase inhibitors can depress behavior in humans and animals, whereas antimuscarinic agents reverse this effect or even produce euphoria. Although these effects have been well documented, the specific brain regions that mediate them remain largely unknown. In the present experiments, muscarinic agonists and antagonists were locally injected into the nucleus accumbens of female Sprague-Dawley rats to test for their effects on behavioral depression in the Porsolt swim test and locomotor activity. Local, microinjections of the drugs in the accumbens elicited behaviors that were similar to the systemic effects reported in other studies. Injection of the non-specific agonist arecoline (40 and 80 microg) dose-dependently inhibited swimming and escape behavior. This may be mediated in part by accumbens M1 receptors because blocking these receptors with the specific antagonist pirenzepine (17.5 and 35.0 microg) did the opposite by increasing swimming. Gallamine (0.13, 0.44, and 0.88 microg), an antagonist at M2 receptors, dose-dependently decreased swimming. Two-way microdialysis suggested that this was in part due to the release of ACh by blocking M2 autoreceptors. Scopolamine, a mixed M1/M2 receptor antagonist, also released ACh but did not decrease swimming, probably because the M1 receptors were blocked; the drug (1.0 microg) increased swimming time, much like pirenzepine. With the exception of arecoline, none of the drugs significantly affected locomotor activity in a photocell cage. Arecoline (40 microg), which had decreased swimming, reduced activity. The present study suggests that muscarinic receptors in the nucleus accumbens can control immobility in the Porsolt swim test. The onset of immobility may depend on the activation of post-synaptic M1 receptors.