Targeted therapies the aim for breast cancer treatment
SummaryDue to more and better screening practices leading to earlier diagnosis, survival rates for breast cancer have risen to as high as 87% in some developed countries. But globally, 380,000 people (mainly women) will still die from breast cancer in 2004. Datamonitor's Fleur Pijpers explains that in the future, new targeted therapies could lead to successful treatment for each individual patient...
Chemotherapy drugs (cytotoxics) are currently the gold standard in breast cancer treatment, and are expected to remain so through until 2008. Antihormonal treatment also remains an option for patients that are suitable, but the future of effective treatment for breast cancer resides with more targeted therapies. This move is largely propelled by the harsh side effects experienced by cancer patients using these current treatments, which include vomiting, nausea, alopecia and fatigue.
Genentech's Herceptin has paved the way for targeted therapies. There are also other similar drugs currently in various stages of clinical trials as more biotechnology companies are specializing in the development of drugs with highly specific target areas. In fact, 68% of breast cancer drugs in the clinical development pipeline are of the innovative, targeted class of drugs.
Another targeted therapy drug, GlaxoSmithKline's Lapatinib is currently in Phase III clinical trials for metastatic breast cancer. Lapatinib is a dual tyrosine kinase inhibitor. The novelty of this drug is that it inhibits two kinases, potentially showing higher efficacy than drugs that target one. It may also effectively combat metastatic disease. This is where the cancer spreads away from the primary tumor site, normally to the lymph nodes and then to the organs, to form secondary tumors.
Cytotoxics and antihormonals serve only to slow the progress of metastatic disease. Curative treatments with lower levels of toxicity for patients with metastatic disease are urgently needed and the advent of drugs with highly specific targets could potentially change this situation, and be very profitable for the pharmaceutical companies concerned.
Datamonitor forecasts that Lapatinib will reach blockbuster status ($1 billion in sales) by 2012 because it is in the highly advantageous position of being the only dual kinase inhibitor in Phase III trials. Approval of the drug should result in high levels of uptake among physicians, whose awareness of signal transduction inhibitors is quite high following Herceptin's success and the press surrounding Iressa, another tyrosine kinase inhibitor that inhibits cancer cell division and growth. However, the predicted arrival on the market of Genentech/Roche's Omnitarg in 2009 will impact Lapatinib's sales.
While the emphasis on treatment for breast cancer is beginning to move away from the traditional cytotoxics and antihormonals, both classes of drugs cannot be ignored because of their proven efficacy. The relatively low proportion of these drugs in the development pipeline, at 22% and 10% respectively, illustrates the move towards more targeted therapies. However, they are far from obsolete and will remain as the standard breast cancer treatment in the near future.
Many cytotoxics in development are reformulations of those currently on the market, in an attempt to decrease toxicity levels and thus the harsh side effects often associated with their use, or to ease their administration.
There are even fewer antihormonals in the pipeline, possibly due to a saturation of the market. AstraZeneca's Nolvadex has recently come off patent, causing a flood of generics onto the market. Even if developed and approved successfully, many new antihormonals are unlikely to capture a significant share of the market. However, these two classes of drugs remain significant, as it is likely that targeted therapies will be used in combination with either.
Decreasing mortality, constant commonality
While the mortality rate for breast cancer is decreasing, it remains the most common form of cancer in women (less than 1% of cases are in men), with an estimated 35,000 new cases expected to be diagnosed in the this year. And while advances in tumor understanding, molecular biology and patient need has caused the breast cancer treatment paradigm to shift away from traditional therapies towards the inclusion of targeted therapies, for the time being cytotoxics and antihormonals will continue to dominate the breast cancer treatment market.
It is widely acknowledged that cytotoxics have reached a plateau in development, associated with limited clinical gain and any further major breakthroughs in treatment restricted to small incremental improvements. The aim of current R&D is to bring to market agents with increased efficacy and decreased toxicity, hence the shift towards targeted therapies.
Despite the rise of targeted therapies, cytotoxics are likely to remain standard treatment for breast cancer until at least 2008. At this point, key breast cancer cytotoxics will start to face patent expiries, which will occur in unison with an increase in physician awareness and acceptance of targeted therapies. Although targeted therapies are unlikely to completely replace cytotoxics, increasingly complex regimens incorporating targeted therapies alongside cytotoxics or antihormonals will become commonplace, as treatment regimens become better tailored to individual patient diseases.