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The Lancet Oncology

Sunday, July 12, 2009

Pemetrexed First Agent Approved in Europe as Maintenance Therapy for Advanced, Nonsquamous Non-Small Cell Lung Cancer

The European Medicines Agency’s (EMEA) Committee for Medicinal Products for Human Use (CHMP) has granted approval for the use of pemetrexed for injection (Alimta ®, Eli Lilly and Company) as monotherapy for maintenance treatment of patients with other than predominantly squamous cell histology in locally-advanced or metastatic non-small cell lung cancer (NSCLC), whose disease has not progressed immediately following platinum-based chemotherapy. This approval is based on data that showed pemetrexed improved overall survival in other than predominantly squamous NSCLC patients in the maintenance setting.

Globally, lung cancer is the most common form of cancer and the biggest killer, causing 1.3 million cancer deaths annually. This is more than breast, colon and prostate cancer taken together. About 85 - 90 percent of all lung cancers are non-small cell lung cancer (NSCLC). Survival rates are very poor.

Major disease forms
Non-small cell lung cancer (NSCLC) is defined as a group of histologies, that is, tumor types differentiated by cellular structure. The most predominant is squamous cell carcinoma (also known as epidermoid carcinoma) which accounts for 30 - 40% of all NSCLC cases. Formed from round cells that replace damaged cells along the epithelium of the main, lobar or segmental bronchi, this disease is a relatively slow growing carcinoma with a relatively good prognosis. Recurrence rates for resected squamous cell carcinoma are relatively low compared top other types of NSCLC, with distant metastases less common given the same treatment at the same stage.

Also referred to as nonsquamous histology, adenocarcinoma, which account for more than half of all NSCLC diagnoses, usually arises from mucus-producing cells of the lung. Aproximately two-thirds of adenocarcinomas develop in the outer regions of the lung, while the remaining one-third develop centrally. The majority of adenocarcinomas are asymptomatic until they have progressed to an advanced stage. As a consequence, the prognosis is generally worse compared to that of squamous cell carcinoma. On the other hand, once diagnosed, adenocarcinomas generally respond better to treatment than other NSCLC histologies.

Squamous cell carcinoma tends to metastasize in the bone, adrenal glands, liver, small intestines and brain. Because this disease is almost always caused by smoking, occurrence has decreased over the past 30 - 35 years.

Other types of NSCLC include bronchoalveolar carcinoma (BAC), a subclassification of adenocarcinoma with distinct clinical and pathologic properties and large cell carcinoma.

The majority of patients with NSCLC eventually develop metastatic disease or disease that is not a candidate for surgical interventions. this makes them potential candidates for systemic therapies. However, the decision on whether a patient receives therapy, greatly depends upon a number of factors, including the disease stage. In general, the more advanced the disease is, the more likely that a physician will prescribe a drug therapy.

Staging of Lung Cancer
Lung Cancer is often classified according to the American Joint Commitee on Cancer (AJCC) TNM staging system, and has five-tier staging, starting at 0 and rising to the severity of stage IV.

The primary T1 tumor, generally smaller than 3 centimeter, is usually easy to define on computed tomography (CT) and fluorodeoxyglucose positron emission tomography (FDG-PET).

TNM stage T3 tumors include tumors of any size with direct extension into the chest wall, diaphragm, mediastinal pleura or pericardium. Stage T4 tumors invade the mediastinum, great vessels, trachea, oesophagus and vertebral bodies.

Lung cancer in metastatic stage becomes aggressive. In this stage a therapy to shrink tumour size, stabilize the disease and relieve debilitating symptoms, with minimal toxic effects of the drug is required. Pemetrexed is the most promising molecule in that aspect. The drug provides better survival, progression free time and response and has superior tolerability than other cytotoxic drugs used for the same condition.

Mechanism of action
Pemetrexed is a multitargeted antifolate currently approved for first-line treatment of advanced, other than predominantly squamous NSCLC in combination with a platinum-based chemotherapy, and as a single agent in the second-line setting for advanced, other than predominantly squamous NSCLC patients with recurrent disease. Pemetrexed is chemically similar to folic acid and is in the class ofchenotheray drugs called folate antimetabolites. It works by inhibiting three enzymes used in purine and pyrimidine synthesis—thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyl transferase (GARFT).

Improve Overall Survival in a Maintenance Setting
The concept of maintenance therapy represents a paradigm shift in the treatment of advanced, other than predominantly squamous NSCLC.
Traditionally, patients who respond to first-line chemotherapy are monitored until the disease recurs and are then treated with a second-line regimen. In maintenance therapy, rather than halting further treatment until disease progression, patients who respond to a first-line therapy are treated immediately with a maintenance regimen.

"The idea behind ALIMTA as maintenance therapy for nonsquamous, non-small cell lung cancer is to treat patients immediately following their initial course of therapy, in an effort to prolong survival," said Richard Gaynor, M.D., vice president, cancer research and global oncology platform leader at Lilly. "The study that led to this approval was the first that showed improved overall survival in the maintenance setting for NSCLC. This was also the third trial to show the benefit of tailoring ALIMTA treatment to the nonsquamous NSCLC patient population."

Overall survival data for pemetrexed as a maintenance therapy for NSCLC was presented on May 31, 2009, at the 45th Annual Meeting of the American Society of Clinical Oncology (ASCO) by Chandra P Belani M.D.

The trial compared efficacy with respect to overall survival of pemetrexed plus best supportive care versus placebo plus best supportive care in 663 patients with stage IIIB/IV NSCLC whose disease had not progressed after four cycles of platinum-based induction chemotherapy. Pemetrexed was not included among the induction regimens studied in the maintenance trial. The trial supported two previous studies looking at the use of histology to tailor treatment for patients with advanced, other than predominantly squamous NSCLC.

Patients in the trial were treated with pemetrexed (500 mg/m2 on day one of each 21-day cycle) plus best supportive care or placebo plus best supportive care. All patients were supplemented with vitamin B12, folic acid and dexamethasone.

Pemetrexed was initially approved by the FDA in 2004 for the treatment of mesothelioma, with subsequent approval for second-line treatment of NSCLC.

This latest approval for pemetrexed - the fourth in Europe - follows an initial positive opinion issued by the European Medicines Agency's (EMEA) Committee for Medicinal Products for Human Use (CHMP) on May 29, 2009, and the recent approval by the U.S. Food and Drug Administration (FDA) of pemetrexed for maintenance therapy in advanced, nonsquamous NSCLC patients whose disease has not progressed after four cycles of platinum-based first-line chemotherapy.

Apart from the existing approvals in the EU and U.S. for the use of pemetrexed in the treatment of patients with locally-advanced or metastatic other than predominantly squamous NSCLC, pemetrexed is also approved, in combination with cisplatin, in both the EU and U.S. for the treatment of chemotherapy naive patients with unresectable malignant pleural mesothelioma.

For more information:
Also read these PubMed abstracts:

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Images courtesy American Society of Clinical oncology (ASCO)

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