Final results from a phase II study presented at ASCO show that 25% of women with advanced HER2-positive breast cancer experienced significant shrinkage of their tumours, when treated with a first in class combination antibody called trastuzumab-DM1 (T-DM1). T-DM1 potentially represents another option for patients with metastatic disease, for which there is no cure.
T-DM1 is potentially a new and highly specialised cancer treatment that combines two approaches to treating cancer in one medicine. It represents the first treatment for breast cancer in a new class of powerful drugs known as antibody-drug conjugates (ADC) - monoclonal antibodies linked with cytotoxic agents that are designed to selectively kill cancer cells. These are results from a phase II study and T-DM1 is not currently licensed in the UK.
The two components of the T-DM1 are: the well-known and proven treatment trastuzumab (Herceptin®), an antibody that specifically targets HER2, and DM1, a chemotherapy treatment. By combining both of these treatments the monoclonal antibody element allows the chemotherapy to be targeted directly to the HER2 genes that encourage the cancer to grow. In this way T-DM1 is able to specifically target cancer cells and maximise clinical benefit, while minimising some of the side effects seen with non-targeted chemotherapy.
Principal UK study investigator for the T-DM1 Phase III study EMILIA, Dr David Miles (Medical Oncologist, Mount Vernon Hospital, UK) said, "These results are welcome news for the thousands of women with advanced HER2-positive breast cancer who have few, if any remaining treatment options. To see such efficacy with one treatment is unusual. It is important that we continue to explore further this promising treatment that takes the drug directly and selectively to kill the cancer cells," Dr Miles said.
In the phase II study approximately 35% of patients either saw their tumours shrink, or their disease stabilised for at least six months. The single-arm, open-label phase II study enrolled 112 patients and was conducted in the US. EMILIA, a global phase III study investigating T-DM1 in patients whose breast cancer has become worse following previous anti-HER2 therapy is ongoing.
Results from the phase I study of TDM-1, presented at ASCO 2008, showed that adverse events, over grade 2, were infrequent and manageable[i].
In addition no cardiac-specific toxicity was observed.
About ASCO
ASCO - the American Society of Clinical Oncology is the world's largest conference on cancer treatments. The annual meeting attracts 37,000 delegates and is renowned as the world's premier cancer conference.
About HER2 positive breast cancer
In 2006, 45,508 women were diagnosed with breast cancer in the UK[ii]. It is thought that about 1 in 5 women with breast cancer will have HER2-positive tumours[iii]. In HER2-positive breast
cancer, increased quantities of the HER2 protein are present on the surface of the tumour cells. This is known as 'HER2 positivity'. This is a distinct form of breast cancer that demands attention because HER2 positive tumours are fast growing and are associated with poor prognosis and a high chance of relapse.
About the Phase II study
The T-DM1 phase II study was a multi-institutional, open-label, single arm trial. The study took place in the United States of America and enrolled 112 women whose breast cancer had progressed following previous treatment with two or more HER2-targeted therapies. The primary endpoint was objective response rate (ORR) as determined by an independent review and the secondary endpoints include:
- duration of response (DoR)
- progression-free survival (PFS)
- clinical benefit rate (CBR)
T-DM1 is the first and only single-agent molecule being studied in a class of investigational agents known as antibody-drug conjugates (ADC) in HER2-positive breast cancer. T-DM1 is made up of trastuzumab (Herceptin), a well-known and proven treatment for HER2-positive cancer, and DM1, a highly potent anti-microtubule derivative. The rationale behind this coupling is to increase the anti-tumour efficacy by bringing trastuzumab and DM1 directly to the cancer cell with limited or no increase in treatment-related side effects. Results from the first phase were presented at ASCO last year.
About EMILIA (phase III study)
Currently a global phase III study (EMILIA) evaluating T-DM1 for second-line advanced HER2-positive breast cancer is ongoing. The 580-patient randomised study was initiated in February 2009 and is comparing single agent T-DM1 to lapatinib plus capecitabine.
References
[i] Beeram et al. A phase I study of trastuzumab-DM1 (T-DM1), a first-in-class HER2 antibody-drug conjugate (ADC), in patients (pts) with advanced HER2+ breast cancer (BC). J Clin Oncol 26: 2008 (May 20 suppl; abstr 1028).
[ii] Cancer Research UK Breast Cancer incidence statistics - info.cancerresearchuk/cancerstats/types/breast/incidence/ Last accessed 27.05.09
[iii] Macmillan Support / Cancerbackup.
cancerbackup.uk/Cancertype/Breast/Causesdiagnosis/HER2testing Last accessed 27.05.09
Source
Roche
View drug information on Herceptin.
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