Gilead’s leukaemia drug Zydelig gains US approval

Gilead’s Zydelig, one of a generation of new treatments set to advance the treatment of chronic lymphocytic leukemia (CLL), has been approved by the FDA.

Zydelig ((idelalisib) is a new oral treatment for three B-cell blood cancers, and promises to reach sales in excess of $1 billion, but will face strong competition from a number of rival treatments.

The three blood cancers are: for use in combination with rituximab in patients with relapsed chronic lymphocytic leukemia (CLL) for whom rituximab alone would be considered appropriate therapy; as monotherapy for patients with relapsed follicular B-cell non-Hodgkin lymphoma (FL); and small lymphocytic lymphoma (SLL) patients who have received at least two prior systemic therapies.

Zydelig is a first-in-class inhibitor of PI3K delta, a protein that is over-expressed in many B-cell malignancies and plays a role in the viability, proliferation and migration of these cancer cells.

Gilead’s drug will compete directly with Imbruvica, marketed by Pharmacyclics and Janssen, which was launched in November last year.

Raksha Mudbhary, Ph.D., GlobalData’s analyst covering Oncology, says: “A number of branded drugs, including Gazyva, Imbruvica, idelalisib and IPI-145, will become available over the next four years, with the expanding patient pool receiving greater access to such new treatments. These factors, alongside dose-continuous regimens replacing fixed courses of therapy, will combine to escalate the CLL market’s value.”

GlobalData forecasts that Imbruvica and Zydelig will have total combined sales of $2 billion in 2018, thus capturing more than 60% of the total CLL market by the end of the forecast period.

Imbruvica and Zydelig have shown strong efficacy and tolerability in phase II and III trials which, combined with the high level of unmet need in these patients, is expected to see rapid uptake of both drugs.

Mudbhary explains: “Furthermore, the completion of trials, as well as the results of studies of Imbruvica and idelalisib in the first-line treatment of elderly patients, which are expected by 2016 and 2017 respectively, will contribute towards establishing these two drugs as the most successful branded therapies for CLL.”

However Zydelig produces serious toxicities which could limit its use. The drug has been linked to fatal and serious liver toxicities of the liver, and it carries a black box warning of severe diarrhoea, colitis, pneumonitis and intestinal perforation, which its rival Imbruvica does not.

Nevertheless, the drug is expected to become another blockbuster product for Gilead, which is already flying high thanks to the unprecedented success of its breakthrough hepatitis C product Sovaldi.


Imbruvica gains approval in CLL


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