Feuerstein on CLDX
@ColfaxCapital asks, "What are your thoughts on $CLDX? In less sick population, ORR should be attainable; PFS goal might be aggressive, unknown?"
Colfax is referring to Celldex Therapeutics and the design for the accelerated approval trial disclosed Thursday morning for its experimental monoclonal antibody drug conjugate CDX-011.
Celldex plans to enroll approximately 300 patients with triple-negative breast cancer with tumors that also over-express the protein GPNMB. [The antibody portion of CDX-011 hones in on GPNMB-expressing tumors.] The patients will be randomized 2:1 to receive treatment with CDX-0-11 or Roche's Xeloda (capecitabine.) The primary endpoints are overall response rate or progression-free survival. Celldex says it will be able to submit for FDA approval (accelerated approval) as long as one of the two endpoints are met.
Celldex chose not to pursue a Special Protocol Assessment (SPA) agreement with FDA for the trial because regulators were copacetic with either overall response (with durability) or PFS as clinically meaningful endpoints given the lack of current treatment options for triple-negative breast cancer, Celldex chief medical officer Tom Davis told me in an interview. Pfizer (PFE_) employed "either/or" primary endpoints for its pivotal trial of the lung cancer drug Xalkori, so there's precedent for this design, added Davis.
The study will begin enrolling patients in the second half of the year, with accrual taking approximately 18 months. Top-line data will likely be approximately nine months later.
In addition to having triple-negative breast cancer that over-expresses GPNMB, the patients in the study will also be resistant to prior treatment with anthracyclines and taxanes. In other words, the patients in the accelerated approval trial will enter with less advanced disease than the patients who participated in the previous phase II study of CDX-011. [I wrote about the results from the CDX-011phase II study when they were presented last December.]
Celldex powered the new study with the assumption that Xeloda-treated patients (the control arm) will have a 15% response rate and PFS of 4 months. The company believes CDX-011 can double response rate to 30% and improve PFS by 2.25 months.
As I write this column on Thursday morning, Celldex shares are down about 5%. Hard to attribute the selling to anything specific, but I know the timelines for the '011 trial are a bit longer than what management told investors during the roadshow leading up to last month's stock offering. (Stock is up 15% today.)
The trial is certainly not without risk, which could also be weighing on the stock. Earlier-stage patients should, theoretically, respond better to CDX-011 but then it's more difficult to use results from the completed CDX-011 trial as an accurate comparator. [And don't forget, the old trial was quite small.]
Cancer drug expert, consultant and blogger Sally Church (@maverickNY) pointed to this study (via Twitter) of Avastin in second-line triple negative breast cancer patients. Median PFS was 6 months for Avastin plus chemotherapy versus 2.7 months for chemotherapy alone.
Church tweeted:
"If Avastin can achieve 6 mon after taxanes in TNBC, then comparing 011 to capecitabine 2nd line will need to match that."
Lots to think about in terms of handicapping the results from the CDX-011 trial. There's also plenty of time.
Celldex is more than just CDX-011. On its call Thursday morning, the company said to expect patient enrollment in the phase III study of rindopepimut in brain tumor patients to wrap at the end of the year. The first interim look at data from the study will take place in mid-2014.
An earlier-stage drug candidate, the complement inhibitor CDX-0135, has also generated some investor interest. A small pilot study in Dense Deposit Disease should have data by year's end.
Bladerunner
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