A Phase 1 study of UCN-01 in combination with irinotecan in patients with resistant solid tumor malignancies

Abstract

Purpose: UCN-01 (7-hydroxystaurosporine) is a multi-targeted protein kinase inhibitor that exhibits synergistic activity with DNA-damaging agents in preclinical studies. We conducted a Phase I study to determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetic, and pharmacodynamic effects of UCN-01 and irinotecan in patients with resistant solid tumors.

Experimental design: Patients received irinotecan (75-125 mg/m(2) IV on days 1, 8, 15, 22) and UCN-01 (50-90 mg/m(2) IV on day 2 and 25-45 mg/m(2) on day 23 and subsequent doses) every 42 days. Blood for pharmacokinetics of UCN-01 and irinotecan, and blood, normal rectal mucosa, and tumor biopsies for pharmacodynamic studies were obtained.

Results: Twenty-five patients enrolled to 5 dose levels. The MTD was irinotecan 125 mg/m(2) on days 1, 8, 15, 22 and UCN-01 70 mg/m(2) on day 2 and 35 mg/m(2) on day 23. DLTs included grade 3 diarrhea/dehydration and dyspnea. UCN-01 had a prolonged half-life and a low clearance rate. There was a significant reduction in SN-38 C(max) and aminopentanocarboxylic acid (APC) and SN-38 glucuronide half-lives. Phosphorylated ribosomal protein S6 was reduced in blood, normal rectal mucosa, and tumor biopsies at 24 h post-UCN-01. Two partial responses were observed in women with ER, PgR, and HER2-negative breast cancers (TBNC). Both tumors were defective for p53. Twelve patients had stable disease (mean duration 18 weeks, range 7-30 weeks).

Conclusion: UCN-01 and irinotecan demonstrated acceptable toxicity and target inhibition. Anti-tumor activity was observed and a study of this combination in women with TNBC is underway.

Fig. 1

Significant decrease in pS6 levels in PBMC following UCN-01 treatment. PBMC were collected at baseline (day 1), 24 h post-irinotecan but prior to UCN-01 (day 2), 24 h post-UCN-01 treatment (day 3) and on day 8 prior to the second irinotecan treatment during cycle 1. PBMC were lysed and analyzed by Western blotting with antibodies specific for S6 ribosomal protein, phosphorylated S6 ribosomal protein (pS6), and actin as a loading control. Representative Western blots of PBMC from three patients are shown (a). The arrow indicates total S6 used for normalization. The ratio of phosphorylated S6 to total S6 protein was plotted for each sample at each time point (b). A natural log transformation of the pS6/S6 ratio was required for a normal distribution for the application of standard parametric tests. After log transformation, a paired t-test (c) and one-way ANOVA (d) were used to assess the differences among different time points (days 1, 2, 3, 8). Homogeneity of pS6/S6 ratio variance was assessed by Leveve’s test, and the variances were found to be equal. A P-value of <0.05 is considered significant and is indicated by **. DF degrees of freedom, N number of samples, CI confidence interval

Fig. 2

UCN-01 decreases pS6 in tumor samples and causes a dramatic response of chest wall lesions to therapy. IHC analysis of pS6 on tumor specimens collected at baseline (a) and 24 h post-UCN-01 therapy (b) from Patient 14, whose tumor carried a somatic mutation in TP53 resulting in a change from CGA (Arginine) to TGA (stop codon) at amino acid 306 (i). Patient 14 had TNBC to the chest wall and lymph nodes and a partial response for 18 weeks. IHC analysis of pS6 on tumor specimens collected at baseline (c) and 24 h post-UCN-01 therapy (d) from Patient 24, whose tumor was ER+ , PR+ , HER2−  and was wild type for TP53 by sequencing. Patient 24 had chest wall and lymph nodes metastasis and disease progression after one cycle of study therapy. Representative fields are shown for each specimen. Specimens from Patient 14 had pS6 intensity scores of 2 for both pre-treatment (a) and post-treatment (b), but the percentage of tumor cells positive for pS6 was significantly decreased, from 20% pre-therapy to 1% post-therapy. Similarly, specimens from Patient 24 had intensity scores of 3 both pre-treatment (c) and post-therapy (d), but the percentage of tumor cells positive for pS6 was significantly decreased, from 40% pre-therapy to 5% post-therapy. IHC analysis of γH2AX on tumor specimens collected at baseline (e) and 24 h post-UCN-01 therapy (f) from Patient 14 and at baseline (g) and 24 h post-UCN-01 therapy (h) from Patient 24 demonstrated more DNA strand double-strand breaks in both tumor samples following combination treatment. Photographs of metastatic breast cancer to the skin from Patient 22 taken at baseline (k) and following completion of 2 cycles of therapy (l). This tumor exhibited nuclear accumulation of p53 by IHC (j) indicative of mutant TP53. Patient 22 had metastatic TNBC to the skin and lymph nodes and experienced a PR for 13 weeks