Development of Angiogenesis Inhibitors

The angiogenic property of thalidomide reported by D'Amato and colleagues has prompted its clinical evaluation in various solid tumors including prostate cancer. Our laboratory previously showed that one of the products of cytochrome P450 2C19 isozyme biotransformation of thalidomide, 5'-OH-thalidomide, is responsible for the drug's antiangiogenic activity. Based on the chemical structure of this metabolite, we have synthesized 118 analogs of thalidomide and have evaluated them using four in vitro models to assess activity in the inhibition of angiogenesis (rat aorta model, human saphenous vein model, cultured endothelial cells, and tube formationassay). We have identified the most potent of these and have patented them. We are continuing to develop these compounds. These compounds appear have minimal side effects in initial preclinical toxicology studies. Using a randomized Phase II trial design we compared weekly docetaxel (30 mg/m2) with or without 200 mg/d of thalidomide. The objective of this study was to determine whether the combination of thalidomide and docetaxel could produce a sufficiently high clinical response rate to warrant further investigation. All of the patients had metastatic AIPC and were progressing on androgen blockade, as well as anti-androgen withdrawal. A total of 75 patients were enrolled onto this trial, 25 patients in docetaxel alone arm and 50 patients in the combination arm. A two-stage mini-max design, that is one in which the design sought to minimize the maximum number of patients enrolled, was chosen for both arms. We used P0=0.25 (undesirable response rate) and P1=0.45 (target response rate) for the combination arm, and P0=0.05 and P1=0.025 for the docetaxel-alone arm, with ?=0.05 and ?=0.10 for both arms. Both at the midpoint evaluation and at the conclusion of the trial, the proportion of patients with a more than 50% decline in PSA was higher in the combination arm (25 of 47 patients, 53%) than in the docetaxel alone arm (9 of 24 patients, 37%). These response rates satisfied criteria for further evaluation (combination arm) and for consistency with prior results (single agent arm). Likewise, 3 of 11 patients (27%) in the docetaxel-alone arm with measurable soft tissue disease by CT scan developed a partial response, and 7 of 20 patients (35%) in the combined treatment group had a partial response in soft tissue disease. None of the patients with bony lesions had a normalization of their bone scan. The median progression free survival was 3.7 mo and 5.9 mo in the docetaxel and combined group, respectively (p=0.32 for the overall difference in the curve). The 18 mo survival was 42.9% in the docetaxel alone group and 68.2% in the combined group. The median overall survival in the docetaxel alone group was 14 mo compared with 28 mo for the combination arm (p=0.11) Thalidomide, Docetaxel, and Estrumustine Based on the positive data we found with the combination of thalidomide and docetaxel, we have recently initiated a Phase II study of estramustine, docetaxel and thalidomide in chemo-naive patients with AIPC. This combination was based on preclinical work done in my laboratory showing synergy with this combination in several xenograft models of prostate cancer. The primary objective of the study is to show a statistically significant improvement in PSA decline when compared to the combination of docetaxel and thalidomide. We are also looking at multiple secondary endpoints. These include possible pharmacokinetic interactions among the study agents, and potential correlation between patient genotype (CYP2C19) and efficacy of treatment. We are also looking for circulating tumor cells in blood before and after treatment. Additionally, we will be monitoring the tolerability of the regimen and survival duration as endpoints. We enrolled 20 patients with metastatic progressive AIPC on to a Phase II clinical trial to evaluate this combination. Docetaxel (30mg/m2) was administered every week, 3 out of 4 weeks. The dose of thalidomide was 200 mg/day and estramustine was given three times a day on Day 1, 2, 3, 8, 9, 10, 15, 16 and 17. We found that the progression free time was 7.2 months with this combination. Ninety percent of patients had a ?50% decline in PSA and 20% of those patients with soft tissue lesions (n=10) had a partial response by CT scan. The regimen has been well tolerated, although there have been several dose reductions of thalidomide and/or estramustine due to side effects (e.g., fatigue, gastrointestinal (GI) complications). There were 24 grade 3 and 2 grade 4 complications associated with this combination. We also found a statistically significant association between overall survival and the CYP1B1*3 genotype (p=0.013). Docetaxel-based chemotherapy is now regarded as standard regimen for metastatic AIPC. In this study, we were able to demonstrate that estamustine, docetaxel and thalidomide proved to be advantageous treatment combination in preclinical models of prostate cancer and is a safe, tolerable and active regimen in patients with AIPC. Dr. Dahut and myself are conducting a Phase II trial of thalidomide, docetaxel, prednisone and bevacizumab in chemo-naive AIPC patients. The primary objective of this study is to determine if this combination is associated with a sufficiently high proportion of patients with a PSA response to be worthy of further investigation. We will also be looking at multiple secondary endpoints, similar to those outlined above for the thalidomide, docetaxel and estramustine trial above. The preliminary results from this study are extremely encouraging. Thalidomide in Stage D0 Androgen Independent Prostate Cancer (ADPC) In 1998, I designed a unique double-blinded randommized Phase III trial to determine if thalidomide could improve the efficacy of LHRH agonists in patients with AIPC, that had a rising PSA level after primary definitive therapy (XRT or radical prostatectomy). Following 6 months of LHRH agonist, patients receive either 200 mg/d of thalidomide or placebo (Phase A). At the time of PSA progression, an LHRH agonist is restarted for 6 additional months. After 6 mo, patients are crossed over to either thalidomide or placebo (Phase B). 154 of 280 patients were enrolled. We recently unblinded the study to find a statistically significant advantage in PFS for the the thalidomide treatment. Development of a High Throughput Screening Assay for the Identification of Novel Inhibitors that Target the HIF System Hypoxia Inducible Factor-1 (HIF-1) is a master transcription factor involved in cellular adaptation to hypoxia. Several small molecules have been found to prevent p300/HIF-1alpha binding. One of these is Chetomin, which has been shown to abrogate the normal interaction and binding of p300/CBP with both HIF-1? and HIF-2alpha in an in-vitro interaction assay, by disrupting the structure and function of p300 CH1. The results also indicated that Chetomin was a specific transcriptional inhibitor, only inhibiting transcription factors that interact with the same face on p300 as HIF-1alpha. These results lead us to screen structurally related compounds, known as ETPs (epidithiodioxopiperazines), in a fluorescence based protein binding assay similar to the Chetomin assay, to examine the structure/activity re [summary truncated at 7800 characters]