Carcinoma In Phase Research Articles

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

711P Outcomes according to genomic characteristics of patients with metastatic urothelial carcinoma in phase I/II trials

Metastatic urothelial carcinoma (mUC) is an aggressive disease with few available therapeutics until recent approval of immune checkpoint inhibitors (ICI), fibroblast growth factor inhibitor receptor inhibitors and antibody-drug conjugate. Nevertheless, some patients do not respond to these treatments and predictive biomarkers are needed, especially for ICI.

Phase IIa study of BVAC-C in HPV type 16 or 18 positive recurrent cervical carcinoma.

5512 Background: BVAC-C is a B cell- and monocyte-based immunotherapeutic vaccine transfected with recombinant HPV E6/E7, which was well tolerated in HPV positive recurrent cervical carcinoma in phase I study (J Clin Med. 2020 Jan 5;9(1):147). This phase IIa study sought to determine the antitumor activity of BVAC-C. Methods: Twenty-one patients with HPV 16 or 18 positive recurrent cervical cancer who had experienced recurrence after one prior platinum-based combination chemotherapy were enrolled. They were allocated to 3 arms; Arm 1, BVAC-C injection at 0, 4, 8 weeks (1x108 cells/dose); Arm 2, BVAC-C injection at 0, 4, 8, 12 weeks (5x107 cells/dose); Arm 3, BVAC-C injection at 0, 4, 8, 12 weeks (5x107 cells/dose) with topotecan at 2, 6, 10, 14 weeks (0.75 mg/m2 for 3 days). Results: The overall response rate was 21% (Arm 1: 29% (2/7), Arm 2: 25% (1/4), Arm 3 : 0 % (0/3)) among the evaluable patients (N = 14), and the median duration of response was 18 months (range, 9 – 26 months). The disease control rate was 43% (Arm 1: 29% (2/7), Arm 2: 50% (2/4), Arm 3 : 67 % (2/3)) and the median duration of stable disease were 12 months (range, 6 - 26 months). The median progression-free survival in all patients was 4 months (95% CI, 2 to Infinite months). Immune responses of patients after vaccination were shown to be correlated with clinical responses of them. Consistent with Phase I study, all evaluated patients showed not only inflammatory cytokine responses (IFN-γ or TNF-α), which might be mediated by the activation of natural killer cells and natural killer T cells, but also potent E6/E7-specific T cell responses upon vaccinations. Conclusions: BVAC-C demonstrated a durable antitumor activity with an immune response in HPV 16- or 18-positive recurrent cervical carcinoma patients who failed 1st line platinum based chemotherapy. Clinical trial information: NCT02866006.

PO32: Impact of Adjuvant Intra Vaginal Brachytherapy in Early Stage Endometrial Cancer

Purpose: Adjuvant treatment with brachytherapy (BT) and/or external beam radiotherapy has reduced the local recurrence rate from 15-26% with surgery alone to <3-6% in intermediate and high risk early-stage endometrial carcinoma in phase III randomized trials. In the current study, we intend to report our outcomes on early stage endometrial cancer patients from a tertiary cancer care center in a developing nation.

1033P - Phase Ib/IIa study assessing the safety and efficacy of adding AL3818 (anlotinib) to standard platinum-based chemotherapy in subjects with recurrent or metastatic endometrial, ovarian or cervical carcinoma

BackgroundAL 3818 (Anlotinib, Catequentinib) is a novel small molecule tyrosine kinase inhibitor that is administered orally. The primary objective of this study is to evaluate the safety, tolerability, and efficacy of adding AL3818, to standard platinum-based plus/or paclitaxel chemotherapy in patients with recurrent or metastatic endometrial, ovarian or cervical carcinoma in Phase 1b/2a studies. MethodsPatients with a diagnosis of recurrent or metastatic endometrial, ovarian, or cervical carcinomas requiring ≥ 2nd line treatment with standard platinum-based chemotherapy were eligible for enrollment on a 21 days cycle. In the Phase 1b study, after chemotherapy at Day 1, patients were started on Day 8 with daily AL 3818 at an initial dose of 12mg for 14 days on a 21day cycle. A 3+3 dose de-escalation design to 10mg, 8mg, and 6mg to determine the recommended Phase II dose (RP2D) was utilized. In the Phase 2a study, patients were treated with the RP2D in combination with either combination platinum based therapy or single agent paclitaxel based on origin of disease. 1st line endometrial patients are allowed. Maintenance monotherapy with AL3818 was given after chemotherapy stopped. ResultsIn the Phase 1b study: (1) 9 subjects with recurrent or metastatic endometrial, ovarian or cervical carcinomas participated with RP2D determined; (2) common treatment emergent adverse event (TEAE) include abdominal pain), alopecia, anemia, arthralgia, asthenia, back pain, and constipation. Overall, most TEAEs were well tolerated by subjects. In Phase 1b and 2a studies: (1) the objective response rate (ORR) and disease control rate (DCR) were 58% and 79% for 19 evaluable endometrial subjects; (2) ORR and DCR were 50% and 93% for all 14 evaluable ovarian subjects; (3) 48 subjects with recurrent or metastatic endometrial, ovarian, and cervical carcinoma were enrolled in the Phase 2a study. ConclusionsAL3818 has demonstrated positive combined synergic efficacy with standard platinum-based plus/or paclitaxel chemotherapy in both endometrial and ovarian cancer patients. Clinical trial identificationNCT02584478. Legal entity responsible for the studyAdvenchen Laboratories, LLC. FundingAdvenchen Laboratories. DisclosureZ. Li: Full / Part-time employment: Advenchen laboratories. M. Chen: Full / Part-time employment: Advenchen laboratories. J. Chen: Full / Part-time employment: Advenchen laboratories. All other authors have declared no conflicts of interest.

Single-Arm Phases 1 and 2 Trial of Niraparib in Combination With Pembrolizumab in Patients With Recurrent Platinum-Resistant Ovarian Carcinoma

Patients with recurrent ovarian carcinoma frequently develop resistance to platinum-based chemotherapy, at which time treatment options become limited. To evaluate the poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor niraparib combined with pembrolizumab in patients with recurrent ovarian carcinoma. The TOPACIO/KEYNOTE-162 (Niraparib in Combination With Pembrolizumab in Patients With Triple-Negative Breast Cancer or Ovarian Cancer) trial, an open-label, single-arm phases 1 and 2 study enrolled women with advanced or metastatic triple-negative breast cancer (TNBC) or recurrent ovarian carcinoma, irrespective of BRCA mutation status. Median follow-up was 12.4 months (range, 1.2 to ≥23.0 months). Data were collected from April 15, 2016, through September 4, 2018, with September 4, 2018, as a data cutoff, and analyzed from September 4, 2018, through January 30, 2019. The recommended phase 2 dose (RP2D) was 200 mg of oral niraparib once daily and 200 mg of intravenous pembrolizumab on day 1 of each 21-day cycle. The primary objectives of phase 1 were to evaluate dose-limiting toxic effects and establish the RP2D and dosing schedule. The primary objective of phase 2 was to assess objective response rate (ORR; complete plus partial responses). Results from the phase 1 ovarian carcinoma and TNBC cohorts and phase 2 ovarian carcinoma cohort are reported. Because of the similarity in the phase 1 and 2 ovarian carcinoma populations, the data were pooled to perform an integrated efficacy analysis. Fourteen patients (9 with ovarian carcinoma and 5 with TNBC) in phase 1 and 53 patients with ovarian carcinoma in phase 2 were enrolled, for a pooled ovarian carcinoma cohort of 62 patients (median age, 60 years [range, 46-83 years]). In the integrated efficacy phases 1 and 2 ovarian carcinoma population (60 of 62 evaluable patients), ORR was 18% (90% CI, 11%-29%), with a disease control rate of 65% (90% CI, 54%-75%), including 3 (5%) with confirmed complete responses, 8 (13%) with confirmed partial responses, 28 (47%) with stable disease, and 20 (33%) with progressive disease. The ORRs were consistent across subgroups based on platinum-based chemotherapy sensitivity, previous bevacizumab treatment, or tumor BRCA or homologous recombination deficiency (HRD) biomarker status. Median duration of response was not reached (range, 4.2 to ≥14.5 months). At data cutoff, 2 patients with a response and 1 patient with stable disease continued to receive treatment. Niraparib in combination with pembrolizumab is tolerable, with promising antitumor activity for patients with ovarian carcinoma who have limited treatment options regardless of platinum status, biomarker status, or prior treatment with bevacizumab. Responses in patients without tumor BRCA mutations or non-HRD cancers were higher than expected with either agent as monotherapy. ClinicalTrials.gov identifier: NCT02657889.

Impact of Hepatitis Virus on the Feasibility and Efficacy of Anticancer Agents in Patients With Hepatocellular Carcinoma in Phase I Clinical Trials.

Chronic viral hepatitis is a risk factor for liver fibrosis and hepatocellular carcinoma (HCC). Patients with advanced HCC have limited effective therapeutic options and are considered potential candidates for early phase clinical trials of anti-cancer agents. The impact of chronic viral hepatitis on the efficacy of anticancer agents for patients with HCC in phase I trials (P-Is) still remains unclear and has not been reported. We retrospectively analyzed the outcomes of consecutive HCC patients in P-Is conducted in a single institute, focusing on chronic viral hepatitis. Of 85 patients enrolled in P-Is, 46 (54%) patients positive and 39 (46%) patients negative for chronic viral hepatitis showed no significant difference in clinical and laboratory variables and on the point of the best response based on the Response Evaluation Criteria in Solid Tumors (RECIST) criteria; moreover, the frequency of Grade ≥3 adverse events (AE) was not significantly different. The median time to treatment failure (TTF) and overall survival (OS) from the P-I enrolment were 2.0 and 13.7 months, respectively. No patient experienced reactivation of hepatitis B virus (HBV) or treatment-related death. Chronic viral hepatitis does not independently affect the outcomes of anticancer drugs. Advanced HCC patients with chronic viral hepatitis could be feasible for P-Is.

53P - Impact of chronic hepatitis virus infection on the feasibility and efficacy for Asian patients with hepatocellular carcinoma in phase I clinical trials

Background: In Asia, chronic hepatitis B and C virus infections (CHVI) are major risk factors for liver fibrosis and hepatocellular carcinoma (HCC). Patients with advanced HCC have limited effective therapeutic options and are potential candidates for early phase clinical trials for new anti-cancer agents. The impact of CHVI on the feasibility and efficacy for patients with HCC in Phase I trials (P-Is) has not been reported or elucidated in Western countries. Methods: We retrospectively analyzed the characteristics and outcomes of HCC patients participating in P-Is, with emphasis on CHVI. Patients testing positive for anti-hepatitis C virus (HCV) antibody or hepatitis B virus surface antigen (HBsAg) were diagnosed with CHVI. Results: Eighty-five patients were enrolled in P-Is at our center. There were no significant differences in the clinical and laboratory variables, including the liver function test results, between the 46 (54%) CHVI-positive and 39 (46%) CHVI-negative patients in this study. The median time to treatment failure (TTF) and overall survivals (OS) from enrollment of the P-I were 60 days (95% confidence interval [CI]: 51–85) and 412 days (95% CI: 267–478), respectively. There is no significant difference between positive and negative for hepatitis virus in the best response based on the RECIST. The frequency of abnormal liver function test (LFT) adverse events (grade ≥ 3) was significantly different among CHVI-positive and -negative patients. No patient discontinued P-I treatment secondary to abnormal LFT results or developed reactivation of hepatitis virus, and no treatment-related mortality was observed. Multivariate analysis revealed that the number of prior systemic treatments significantly contributed to poor TTF (≥2; HR: 2.1, 95% CI: 1.3–3.6, P = 0.004) and that poor Eastern Cooperative Oncology Group Performance Status significantly contributed to poor OS (≥1; HR: 1.9, 95% CI: 1.0–3.4, P = 0.04). Conclusions: CHVI did not independently predict TTF and OS. Abnormal LFT adverse events could be related to CHVI but did not lead to discontinuation of P-I treatment. Thus, patients advanced HCC with CHVI can be enrolled in the P-Is. Legal entity responsible for the study: N/A Funding: Has not received any funding Disclosure: All authors have declared no conflicts of interest.

Efficacy observation of surgical operation combined with neoadjuvant concurrent chemoradiotherapy before operation for middle and lower rectal carcinoma in phase II and III

Objective To explore the application value of surgical operation combined with neoadjuvant chemoradiation therapy for rectal carcinoma in phase Ⅱ and Ⅲ and to evaluate the effect of surgical resection. Methods A retrospective analysis was performed from January 2012 to January 2017, including 70 cases of middle and lower rectal carcinoma in phase Ⅱ and Ⅲ in the First Affiliated Hospital of Hebei North University. Neoadjuvant concurrent chemoradiotherapy before operation was applied. Neoadjuvant radiotherapy: total dose 50 Gy, 2.0 Gy for once, 5 times per week, 5 weeks in total, the radiation field 5 wild for pelvic irradiation. Neoadjuvant chemotherapy: XELOX (oxaliplatin, capecitabine)/ FOLFOX (oxaliplatin, leucovorin, 5-fluorouracil) was used for synchronous chemotherapy. After radiotherapy, the patients received surgery in 6-8 weeks. All the operations were performed according to the total mesorectum excision (TME) specification. Results A total of 70 patients underwent neoadjuvant concurrent chemoradiotherapy. The adverse effect rate was 15.71% (11/70) of grade Ⅰ and 7.14% (5/70) of grade Ⅱ. No grade Ⅲ and Ⅳ adverse reactions occurred. The tumor stage of 94.29% (66/70) patients reduced. The TNM stage of the postoperation was decreased compared with that before neoadjuvant chemoradiotherapy (χ2= 7.846, P < 0.05). Tumor resection rate was 94.29% (66/70). Conclusion Surgical operation combined with neoadjuvant concurrent chemoradiotherapy before operation for middle and lower rectal carcinoma in phase Ⅱ and Ⅲ has a favorable efficacy and safety, which can alleviate the tumor staging and increase the eradication rate of tumors. Key words: Rectal neoplasms; Chemotherapy, adjuvant; Radiotherapy, adjuvant; Total mesorectal excision

Abstract 3264: Lenvatinib in combination with everolimus demonstrated enhanced antiangiogenesis and antitumor activity in human RCC xenograft models

Abstract Lenvatinib mesilate (lenvatinib) is an oral multiple receptor tyrosine kinase (RTK) inhibitor that selectively inhibits the kinase activities of vascular endothelial growth factor (VEGF) receptors VEGFR1 (FLT1), VEGFR2 (KDR), and VEGFR3 (FLT4), in addition to other proangiogenic and oncogenic pathway-related RTKs including fibroblast growth factor (FGF) receptors FGFR1, 2, 3, and 4; the platelet-derived growth factor (PDGF) receptor PDGFRα; KIT; and RET. Lenvatinib showed antitumor activity against various tumor types mainly through its potent inhibition of angiogenesis, and is currently marketed for the treatment of patients with radioactive iodine-refractory differentiated thyroid cancer. Recently, lenvatinib in combination with everolimus has shown longer progression free survival compared to lenvatinib or everolimus alone in renal cell carcinoma in Phase 2 study. The aim of this study is to elucidate the activity of the combination of lenvatinib and everolimus in preclinical human RCC xenograft models. We examined antitumor activity in two human RCC (A-498 and Caki-1) xenograft models orally treated with lenvatinib (10 mg/kg), everolimus (30 mg/kg), and the combination of lenvatinib and everolimus for 1 or 2 weeks. The antitumor proliferation and antiangiogenic effects were evaluated by immunohistochemistry (IHC) using anti Ki67 antibody and anti CD31 antibody, respectively. The induction of apoptosis was detected by TUNEL assay. To analyze the gene expression profile of tumor samples, microarray analysis were also conducted. The antitumor activity of the combination of lenvatinib and everolimus was greater than that of either agent administered alone in A-498 and Caki-1 xenograft models. The combination caused tumor regression and had no remarkable body weight loss. IHC analysis revealed decrease of microvessel density in lenvatinib and combination groups, and also decrease in the proportion of proliferative cells in everolimus treated and combination-treated group in A-498 model. In TUNEL assay, significant induction of apoptosis was observed only in the combination-treatment group. The analysis of gene expression profile in A-498 xenograft tumors also supported these results: lenvatinib alone upregulated hypoxia-related genes and everolimus decreased proliferation-related genes. The combination of these 2 drugs induced blends of the gene expression changes caused by each single treatment. Our results indicate that treatment of lenvatinib in combination with everolimus caused significant antitumor effect by combining the potent antiangiogenic activity of lenvatinib as well as direct antitumor activity of everolimus in A-498 model. These preclinical results provide one of the mechanisms to support the significant clinical benefit observed in RCC with the combination of lenvatinib and everolimus. Citation Format: Yusuke Adachi, Masahiro Matsuki, Atsumi Yamaguchi, Yoichi Ozawa, Kiyochi Okamoto, Kaoru Mitsuhashi, Takayuki Kimura, Taisuke Hoshi, Osamu Tohyama, Kenji Tai, Makoto Ogo, Yasuhiro Funahashi, Junji Matsui. Lenvatinib in combination with everolimus demonstrated enhanced antiangiogenesis and antitumor activity in human RCC xenograft models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3264.

Targeted Cancer Therapy Using Engineered Salmonella typhimurium.

Obligate or facultative anaerobic bacteria such as Bifidobacterium, Clostridium, Salmonella, or Escherichia coli specifically colonize and proliferate inside tumor tissues and inhibit tumor growth. Among them, attenuated Salmonella typhimurium (S. typhimurium) has been widely studied in animal cancer models and Phase I clinical trials in human patients. S. typhimurium genes are easily manipulated; thus diverse attenuated strains of S. typhimurium have been designed and engineered as tumor-targeting therapeutics or drug delivery vehicles that show both an excellent safety profile and therapeutic efficacy in mouse models. An attenuated strain of S. typhimurium, VNP20009, successfully targeted human metastatic melanoma and squamous cell carcinoma in Phase I clinical trials; however, the efficacy requires further refinement. Along with the characteristics of self-targeting, proliferation, and deep tissue penetration, the ease of genetic manipulation allows for the production of more attenuated strains with greater safety profiles and vector systems that deliver designable cargo molecules for cancer diagnosis and/or therapy. Here, we discuss recent progress in the field of Salmonellae-mediated cancer therapy.

Systemic PD-1/PD-L1 inhibition combined with local vascular-targeted photodynamic therapy (VTP): Effects on primary tumor and prevention of lung metastasis in a preclinical RCC model.

477 Background: Immune checkpoint inhibitors targeting the PD-1 pathway have shown activity against advanced renal cell carcinoma in phase 2 clinical trials. The response to PD-1 inhibition is not consistent however and may depend on host factors (ie. PD-L1 expression). Strategies that modulate immune regulation in the tumor microenvironment can impact responses to PD-1 pathway inhibitors. We have previously shown that VTP treatment of primary tumors using the novel photosensitizer WST-11 induces a defined local inflammatory response. We sought to evaluate whether response to PD-1/PD-L1 inhibition could be enhanced with VTP treatment of primary tumors. Methods: Balb/c mice bearing orthotopically implanted Renca kidney tumors were treated with IgG alone, anti-PD-1/anti-PD-L1 monoclonal antibodies (mAbs), VTP alone, or VTP + mAbs. VTP treatment of the primary tumor was performed 10 days (d10) after tumor implantation. Primary tumor response, enumeration of lung metastases and histologic analysis was performed on d21. Results: Treatment of the primary tumor with VTP and systemic PD-1/PD-L1 inhibition (n=15) resulted in regression of primary tumors whereas PD-1/PD-L1 inhibition alone (n=21) or VTP treatment alone (n=16) did not (no gross tumor vs. median tumor size 96mm2 vs 36 mm2 vs 81 mm2for combination vs mAbs alone vs VTP alone vs control, p&lt;0.0001). Significant treatment effect was also observed in the combined treatment group by histologic analysis. Furthermore, growth of lung metastases was prevented with the combined treatment regimen compared to either treatment alone (median number lung mets=3 vs 56 vs 53 vs 23 for combination, mAb alone, VTP alone and control, respectively, p=0.0252). Conclusions: Only the combination of systemic PD-1/PD-L1 inhibition and local VTP provided primary tumor control and prevention of distant metastasis. Modulation of the inflammatory response in the tumor microenvironment with local therapy such as VTP may enhance the effects of systemic PD-1/PD-L1 blockade to provide better local and metastatic tumor control that can be investigated in prospective clinical trials.

CpG island methylation, response to combination chemotherapy, and patient survival in advanced microsatellite stable colorectal carcinoma

The CpG island methylator phenotype (CIMP) is a distinct epigenetic phenotype in colorectal carcinoma with concordant methylation in multiple promoter CpG islands. The relationship between CpG island methylation and clinical outcomes among colorectal cancer patients treated with chemotherapy has been a controversial subject. Utilizing real-time polymerase chain reaction (PCR; MethyLight technology), we quantified DNA methylation in 13 CpG island loci (CACNA1G, CDKN2A, CRABP1, IGF2, MLH1, NEUROG1, RUNX3, SOCS1, MINT1, MINT31, IGFBP3, MGMT, and WRN) in 30 metastatic microsatellite stable colorectal carcinomas in phase I/II clinical trials of combination chemotherapy (5-fluorouracil, irinotecan, leucovorin, and gefitinib). Tumor response was assessed by CT scans performed at baseline and every 6 weeks thereafter. Overall CIMP-high status (either >or=9/13 or >or=7/13 methylated markers; identifying 3 or 5 CIMP-high tumors, respectively) and methylation in CACNA1G, IGF2, MLH1, NEUROG1, RUNX3, MINT31, and WRN were associated with worse survival (all p < 0.01). Although not statistically significant, there was a trend toward resistance to chemotherapy among tumors with CpG island methylation. In conclusion, CpG island methylation may predict poor survival in metastatic microsatellite stable colorectal carcinoma treated with chemotherapy. Additional studies are necessary to examine the role of DNA methylation in treatment efficacy.

794 ORAL Randomized Phase III trial of the multi-kinase inhibitor sorafenib (BAY 43–9006) in patients with advanced renal cell carcinoma (RCC)

Activating mutations in Ras and B‐RAF were identified in several human cancers. In addition, several receptor tyrosine kinases, acting upstream of Ras, were found either mutated or overexpressed in human tumors. Because oncogenic activation of the Ras/RAF pathway may lead to a sustained proliferative signal resulting in tumor growth and progression, inhibition of this pathway represents an attractive approach for cancer drug discovery. A novel class of biaryl urea that inhibits C‐RAF kinase was discovered using a combination of medicinal and combinatorial chemistry approaches. This effort culminated in the identification of the clinical candidate BAY 43‐9006 (Sorafenib, Nexavar®), which has recently been approved by the FDA for advanced renal cell carcinoma in phase III clinical trials. Sorafenib inhibited the kinase activity of both C‐RAF and B‐RAF (wild type and V600E mutant). It inhibited MEK and ERK phosphorylation in various cancer cell lines and tumor xenografts and exhibited potent oral antitumor activity in a broad spectrum of human tumor xenograft models. Further characterization of sorafenib revealed that this molecule was a multikinase inhibitor that targeted the vascular endothelial growth factor receptor family (VEGFR‐2 and VEGFR‐3) and platelet‐derived growth factor receptor family (PDGFR‐β and Kit), which play key roles in tumor progression and angiogenesis. Thus, sorafenib may inhibit tumor growth by a dual mechanism, acting either directly on the tumor (through inhibition of Raf and Kit signaling) and/or on tumor angiogenesis (through inhibition of VEGFR and PDGFR signaling). In phase I and phase II clinical trials, sorafenib showed limited side effects and, more importantly, disease stabilization. This agent is currently being evaluated in phase III clinical trials in renal cell and hepatocellular carcinomas.

Taxol: A Novel Investigational Antimicrotubule Agent

Microtubules are among the most strategic subcellular targets of anticancer chemotherapeutics. Despite this fact, new antimicrotubule agents that possess unique mechanisms of cytotoxic action and have broader antineoplastic spectra than the vinca alkaloids have not been introduced over the last several decades--until the recent development of taxol. Unlike classical antimicrotubule agents like colchicine and the vinca alkaloids, which induce depolymerization of microtubules, taxol induces tubulin polymerization and forms extremely stable and nonfunctional microtubules. Taxol has demonstrated broad activity in preclinical screening studies, and antineoplastic activity has been observed in several classically refractory tumors. These tumors include cisplatin-resistant ovarian carcinoma in phase II trials and malignant melanoma and non-small cell lung carcinoma in phase I studies. Taxol's structural complexity has hampered the development of feasible processes for synthesis, and its extreme scarcity has limited the use of a conventional, broad-scale screening approach for evaluation of clinical antitumor activity. However, taxol's unique mechanism of action, its spectrum of preclinical antitumor activity, and tumor responses in early clinical trials have generated renewed interest in pursuing its development.