Yesterday afternoon, the FDA and ODAC met for a second time in the day to review the application for omacetaxine from ChemGenix. The drug was tested in limited trials in people with chronic myeloid leukemia (CML) for whom tyrosine kinase (TKI) therapy with drugs such as imatinib, dasatinib or nilotinib had failed or who had the T315i mutation.
My previous analysis from last month is here. Unlike the concerns in the morning with safety and efficacy associated with pixantrone in NHL, this time the FDA were clearly concerned about the validity of commercially available assays to detect the T315i mutation.
I did a search to see what was out there for testing T315i and found two:
- Quest Diagnostics are advertising one here.
- DxS Diagnostics are advertising one here.
Interestingly, the DxS one clearly states that it is for research purposes only, not for diagnosis. I'm not sure if the Quest test has been approved commercially, but it would seem odd of the FDA to make a song and dance about a widely available test if there is one available, so it is possible that both are only available for research purposes so far and as such, not approved for commercial use. Or it may be that the Quest one is approved but has not yet been validated with omacetaxine. It isn't overly clear from the information we have so far.
Either way, Kerri Wachter was on the scene at the meeting and tweeted the vote succinctly:
This isn't really surprising: if you are claiming to target a particular marker or target, then you need a validated companion diagnostic test to be commercially available once the drug is approved. I think what the FDA is saying to ChemGenex is that they need to do a small study comparing and validating the data between commercial assays and the ones used more commonly in hospital Path labs for research purposes and clinical trials. It's not a big deal, but it does need to be done.