Yesterday brought two new approvals in a day from the FDA in completely different cancer types.

In the morning, sanofi-aventis' cabazitaxel (Jevtana) was approved in castrate-resistant prostate cancer after failure of docetaxel (Taxotere) several months ahead of schedule.  This approval comes hot on the heels of Dendreon's sipuleucel-T (Provenge) in asymtomatic metastatic prostate cancer last month.

What this means is that once androgen ablation therapies stop working, there are three new treatment options for men with prostate cancer, none of which compete with each other, with the possible exception of the chemotherapies, since docetaxel is often given in second-line in men who previously responded well and have had a treatment break.  It will be interesting to see if this approach continues or if oncologists will prefer cabazitaxel in those with a good performance status.

The real impact of cabazitaxel though, is on other agents in development. Currently, abiraterone (Cougar Biotech/J&J) and MDV3100 (Medivation/Astellas) were being tested in docetaxel refractory prostate cancer, but now there is a new standard of care, whereas previously there was none.  Clearly, common sense suggests that their role might be more impactful earlier in the disease, either after hormonal therapies fail, instead of or in combination with them, especially given that they are oral therapies, making them attractive to urologists. 

Classic drug development usually means starting in the relapsed or refractory metastatic setting. The next few years will be thus be interesting to watch, especially if the agents in clinical trials prove successful. For now, Dendreon have a couple of years breathing space until the market potentially starts to get more crowded.

The other Priority approval yesterday was for Novartis' nilotinib (Tasigna) in newly diagnosed chronic myeloid leukemia (CML) on the basis of higher and earlier response rates versus the current standard of care, imatinib (Gleeevc). Full approval follows later once the survival data is more mature, but the early 12 month data looks interesting with a significant advantage to nilotinib over imatinib. It's still early though, survival curves can do strange things over time and can cross over. 

Still, it's a promising start and a good result, especially since the bar was raised very high by imatinib. Prior to imatinib, ten year survival in CML was 10 to 20% at best with high dose interferon, but imatinib raised that dramatically to 90%. The second generation TKIs such as nilotinib and dasatinib (BMS) will thus potentially represent incremental survival improvements to 93 or 94%, to put them in context.

Of course, nilotinib's approval will possibly impact dasatinib (Sprycel) since they have just filed for the same indication, making Priority review more unlikely. The last time that happened to two drugs in the same cancer type was for Erbitux (ImClone) and Avastin (Genentech), who filed a few weeks apart, but in two different indications (newly diagnosed and 3rd line).  

If dasatinib does get a Priority review after nilotinib it will set a new precedent, but if it doesn't get Priority review, I wonder if an ODAC will occur given that's usually what happens with standard 12 month review?  

What's fascinating about the dasatinib data is that it also demonstrated earlier and deeper responses than imatinib, but the front-line data presented by Drs Kantarjian and Baccarani at ASCO and EHA respectively, did not appear to show any earlier survival benefit at 12 months for dasatinib vs imatinib, unlike nilotinib. I say 'appear' because the curves were very close together and no P value was given, so my assumption is that they weren't significantly different at this stage. That may change over time, but for now, the DASISION data presented by Dr Kantarjian showed a 12 month OS of 97.2% to dasatinib and 98.8% to imatinib, presumably not a significant difference. Deaths in the two arms were 10 and 6 respectively, again favouring imatinib, but not significantly. 

Obviously, comparing these curves at 5 years would be a much fairer comparison for overall survival, but for now, the 12 month data is all we have to go on and there are early differences between nilotinib and dasatinib.  

It was also interesting to watch the often hyped and inelegant reporting of the data by the media at the Congresses proclaiming superiority. We know that in solid tumours, shrinkage or tumour response does not always lead to an improved survival benefit for the patient. Similarly, in leukemia, we also measure response rates – in this case – complete cytogenetic response (CCyR), major molecular response (MMR) and complete molecular response (CMR), as initial surrogate markers for initial approval, but survival is also critically important for full approval in the US. Interestingly, the early log 4 reduction (CMR) rates seemed to slightly favour nilotinib over imatinib (but not significantly), however none were presented at ASCO or EHA for dasatinib over nilotinib (unless I missed the slides).

Ultimately, ASH will herald the 2-year and 18-month data for nilotinib and dasatinib respectively, which will hopefully be an important milestone on the way to seeing how the mature five year surviv
al data will evolve.
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Disclosure:  I'm a former Novartis employee and marketing director for Gleevec, so naturally I'm slightly biased towards imatinib :).  Many thanks to @erohealth for proofreading suggestions.