Promising Results From Phase 2 Clinical Trial Of Xcytrin

Armen Hareyan's picture

Pharmacyclics announced promising preliminary results from an open-label Phase 2 clinical trial of Xcytrin Injection, the company's lead cancer therapeutic candidate.

It is a second-line treatment for patients with recurrent, metastatic non-small cell lung cancer who failed at least one platinum-based chemotherapy regimen.

The results were published in the proceedings of the 2007 American Society of Clinical Oncology Annual Meeting (ASCO) taking place this week in Chicago.

"These results indicate that Xcytrin is an active, well-tolerated drug for treatment of recurrent NSCLC," said Richard A. Miller, M.D., president and CEO of Pharmacyclics. "The response rate and survival observed in this trial are comparable to currently approved second-line therapies for NSCLC and support our strategy to conduct multiple ongoing Phase 2 studies of Xcytrin in combination with standard therapies and move into a pivotal trial for this indication early next year. In addition, we are continuing to pursue our new drug application for Xcytrin to treat patients with brain metastases from NSCLC. We believe Xcytrin's selectivity, novel mechanism of action, magnetic resonance imaging detectability, and non-overlapping toxicity with other agents make it an appealing drug to study in combination with other therapies for a broad range of cancers."


The abstract, "A phase II trial of motexafin gadolinium (MGd) in advanced non-small cell lung cancer (NSCLC) patients who had failed platinum-based chemotherapy: Preliminary results of Stage 1," described interim results from a Phase 2 trial evaluating the safety, tumor response and duration of response in patients with recurrent NSCLC who are treated with Xcytrin. Patients in the trial are randomized to receive either a 10mg/kg dose of Xcytrin every week, or a 15mg/kg dose every three weeks. Tumor response rate is being evaluated using Response Evaluation Criteria in Solid Tumors (RECIST), the standard parameters used to document response for solid tumors.

Of 58 evaluable patients there was a confirmed response rate of 5.2%, or three partial responses. Twenty patients (34.5%) had stable disease. One of the responders received Xcytrin after having progressed through two prior lines of therapy: carboplatin, gemcitabine and bevacizumab, followed by erlotinib. The other two had previously failed either carboplatin/gemcitabine or cisplatin/vinorelbine. Median time to progression was seven weeks for all patients. Twenty (34.5%) patients received four or more cycles of Xcytrin, of whom seven did not respond to first line chemotherapy. Thirteen percent were free from progression at six months. Median survival was eight months, with 62% and 30% of patients alive at 6 and 12 months, respectively. Xcytrin was well-tolerated in this study. The most common grade 3 or 4 adverse events were hypophosphatemia (24%), dyspnea (12%), fatigue (10%), hypoxia (7%), and finger blisters (5%).

The American Cancer Society predicts that there will be more than 213,000 new cases of lung cancer in the U.S. in 2007. Lung cancer is the leading cause of cancer death, and accounts for over 160,000 deaths in the U.S. each year. The most common form of lung cancer, non-small cell, is incurable in advanced stages. Lung cancer frequently spreads to other body parts, including the brain.

Pharmacyclics is developing Xcytrin as an anti-cancer agent with a novel mechanism of action that is designed to selectively concentrate in tumors and induce apoptosis (programmed cell death). Xcytrin is a redox-active drug that has been shown to disrupt redox-dependent pathways in cells and inhibit oxidative stress related proteins such as thioredoxin reductase. Its multifunctional mode of action, including its magnetic resonance imaging detectability, provides the opportunity for Xcytrin to be used in a broad range of cancers. In previously conducted randomized trials, Xcytrin combined with whole brain radiation therapy (WBRT) has been shown to prolong time to neurologic progression in patients with brain metastases from NSCLC.

The target for Xcytrin is the enzyme thioredoxin reductase, which is frequently over expressed in lung cancer cells. This enzyme has been shown to confer to cancer cells characteristics of aggressive tumor growth and resistance to chemotherapy. First line therapy for advanced NSCLC includes combination chemotherapy using drugs such as carboplatin, cisplatin, Gemzar (gemcitabine), taxanes and others. Currently approved agents for second-line treatment of NSCLC include Alimta (pemetrexed), Tarceva (erlotinib) and Taxotere (docetaxel), which have tumor response rates ranging from 4-10%.

Xcytrin, either in combination with Alimta or Taxotere, is now being evaluated in two other ongoing Phase 2 trials as second-line therapy for NSCLC. Interim data from these trials will be presented in late June at the International Lung Cancer Congress Meeting.