Merck’s immunotherapy drug Keytruda can now be sold as a
first-line therapy for certain metastatic non-small cell lung cancer (NSCLC) patients —
an industry-first that once again shifts the balance of power in the
anti-PD-L1 therapy duel.
The news reverberated throughout the biopharma field, largely due to the
backstory of the immunotherapies. Keytruda has long been jostling for
market share with Opdivo, a PD-L1 inhibitor from Bristol-Myers Squibb.
Both were approved for use in patients with melanoma
just weeks apart in 2014.
Total sales of Keytruda in 2015 reached
$566 million, compared to $942 million by Opdivo. However, following Monday’s
Bernstein analysts forecast an additional $1 billion in sales for Keytruda in 2017.
Another analyst agreed.
“Keytruda 3Q sales were slightly below our and consensus estimates;
however, we are raising our forecasts in expectation of a sharp acceleration
following last night’s approval in the first-line non-small cell
lung cancer (NSCLC) setting,” wrote,” wrote Leerink Partners
analyst Seamus Fernandez in an
investor note late Monday.
Both Keytruda and Opdivo are checkpoint inhibitors, which work to rally
the patient’s immune system against certain tumor cells by blocking
the immune-suppressing PD-L1 pathway. Not all tumor cells express PD-L1,
which is why the FDA has outlined a number of restrictions for Keytruda’s
use as a first-line therapy.
Chief among them is the need for a companion diagnostic to determine if
the patient’s tumor has high levels of PD-L1 (>50%). Agilent
Technologies supplies the
companion diagnostic used by both Opdivo and Keytruda to quantify relative levels.
In a sign that we perhaps don’t know all that much about the mechanisms
of action, the FDA has also approved Keytruda as a secondary treatment
for patients with NSCLC that have unsuccessfully tried chemotherapy. The
cut-off in this instance is a tumor proportion score (TPS) of greater
than 1 percent.
interview with MedCity News in August, oncologist Timothy Byun of the Center for
Cancer Prevention and Treatment at St. Joseph Hospital in Orange, California,
described the lack of consensus.
“There’s three or four PD-L1 immunohistochemical probes and
they are not all the same. Merck has one probe and BMS used their own
probe that was different than the Merck probe,” he said. “And
it’s not comparing apples to apples. You don’t know if the
50% staining on the tumor cells correlates to a 50% staining using another
probe. And to further complicate the matter, you don’t know whether
you should be testing and looking for the PD-L1 staining in the cancer
cell or the immune cells or both.”
The PD-L1 variables can apparently go both ways. Keytruda’s approval
comes just 80 days after news broke of Bristol-Myers’failed phase III trial of Opdivo as a first-line therapy for NSCLC. The upset caused Bristol-Myers
shares to plummet 16%, while Merck’s climbed 8.7% as its market opportunity expanded.
Interestingly, the FDA completed its review of Keytruda two months earlier
than expected. For the industry, this is rare. However, as Fernandez of
Leerink Partners pointed out in his
investor note, Bristol-Myers Squibb gained a series of approvals for Opdivo more than
3 months before the reviews were due.
Kenilworth, New Jersey-based Merck now has an 11-year window to maximize
sales while Keytruda remains under patent protection.
Photo: Kena Betancur, Getty Images