Despite oncology pipelines being the richest in the industry, failures
to translate successful phase 2 studies into phase 3 successes
underline the need for greater innovation in the design and practice
of cancer trials. Last month, the US Food and Drug Administration
(FDA) issued draft guidance for its accelerated approval program, proposing
that patients with highly aggressive breast cancers be eligible
to receive novel experimental therapies for a few months. Permitting
treatment-naive patients to receive experimental therapy first-line is a
radical departure from conventional first-in-human studies, which have
always tested new treatments in patients with advanced or metastatic
disease that has failed to respond to available treatment options. As such,
this initiative from the FDA is a welcome change that may facilitate the
identification of cancer treatments with the potential to prolong survival
for patient groups poorly served by existing therapies.
This issue of Nature Biotechnology surveys some of the most promising
technologies currently being developed to interrogate cancer biology.
They range from single-cell analysis approaches and genetically engineered
mouse models to areas of new target discovery and experimental
treatment modalities, such as oncolytic viruses. Deep sequencing and
cancer genomics are broadening our understanding of the key genetic
and epigenetic events in tumor initiation, progression and metastasis.
Genome-wide studies are beginning to reveal unprecedented genetic
and epigenetic heterogeneity within individual cancers, including population
diversity in mutations involving putative driver loci. With these
rapid advances in technology and our understanding of cancer genetics
and biology, it is thus striking just how pedestrian progress remains in
the clinic.
Today, setting up a cancer trial can take anywhere from six months
to two years. By the time the trial commences, the agents being tested
can already be outmoded—for example, many of the oncolytic viruses
currently in human testing are using older generation constructs. One
reason why cancer trials take such a long to time to get up and running
is patient recruitment. Although an estimated 20% of adult cancer
patients are medically eligible to participate in a clinical trial, concerns
over quality-of-life issues and insurance reimbursement mean that
accrual rates remain at the staggeringly low level of ~3%—and these
rates are even lower for minorities and young adult cancer patients with
high mortality rates.
As the standard of care improves for a cancer, the threshold for proving
efficacy also rises making it more difficult to prove a new drug will extend
patient survival. Regulators, in some cases, do consider alternatives to the
gold-standard endpoint of overall survival, which requires conducting a
trial for sufficient time to demonstrate a percentage of study subjects have
survived for a defined period of time. Pfizer’s Xalkori (crizotinib), for
example, was approved for metastatic lung cancer based on an assessment