Liposomal Formulations
Doxil is a pegylated (polyethylene glycol coated) liposome-encapsulated form of doxorubicin formerly made by Ben Venue Laboratories in the United States for Janssen Products, LP, a subsidiary of Johnson & Johnson. It was developed to treat Kaposi's sarcoma, an AIDS-related cancer that causes lesions to grow under the skin, in the lining of the mouth, nose and throat, or in other organs. The polyethylene glycol coating results in preferential concentration of Doxil in the skin. However, this also results in a side effect called palmar plantar erythrodysesthesia (PPE), more commonly known as hand-foot syndrome. Following administration of Doxil, small amounts of the drug can leak from capillaries in the palms of the hands and soles of the feet. The result of this leakage is redness, tenderness, and peeling of the skin that can be uncomfortable and even painful. In clinical testing at 50 mg/m2 dosing every 4 weeks, 50.6% of patients treated with Doxil developed hand-foot syndrome. The prevalence of this side effect limits the Doxil dose that can be given as compared with doxorubicin in the same treatment regimen, thereby limiting potential substitution. Substitution would be desirable because liposome-encapsulated doxorubicin is less cardiotoxic than unencapsulated doxorubicin. Doxil is also approved by the FDA for treatment of ovarian cancer and multiple myeloma. Outside the United States, Doxil is known as Caelyx and is marketed by Janssen.
Myocet is a non-pegylated liposomal doxorubicin made by Enzon Pharmaceuticals for Cephalon in Europe and for Sopherion Therapeutics in the United States and Canada. Myocet is approved in Europe and Canada for treatment of metastatic breast cancer in combination with cyclophosphamide, but is not yet approved by the FDA for use in the United States. It is currently being studied by Sopherion Therapeutics in a pivotal phase III global registrational trial in concurrent combination with trastuzumab (Herceptin) and paclitaxel (Taxol) for treatment of HER2-positive metastatic breast cancer. Unlike Doxil, the Myocet liposome does not have a polyethylene glycol coating, and therefore does not result in the same prevalence of hand-foot syndrome. The minimization of this side effect may allow for one for one substitution with doxorubicin in the same treatment regimen, thereby improving safety with no loss of efficacy. Like Doxil, the liposomal encapsulation of the doxorubicin limits the cardiotoxicity. In theory, by limiting the cardiotoxicity of doxorubicin through liposomal encapsulation, it can be used safely in concurrent combination with other cardiotoxic chemotherapy drugs, such as trastuzumab. There is an FDA black box warning that Herceptin cannot be used in concurrent combination with doxorubicin, only in sequential combination. Though concurrent combination of trastuzumab and doxorubicin in clinical studies found superior tumor response, the combination resulted in unacceptable cardiotoxicity, including risk of cardiac failure manifesting as congestive heart failure (CHF). Published phase II study results have shown that Myocet, trastuzumab, and paclitaxel can safely be used concurrently without the cardiac risk, as measured by reduction in LVEF function, while still achieving superior tumor response. This finding is the basis for the on-going phase III trial for FDA approval.
Read more about this topic: Doxorubicin, Clinical Use