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If you've followed my news coverage for the week, then I imagine you're getting a little bit bored of acute myeloid leukemia (AML) stuff. There has been an absolute blitz of approvals and other news coming out for this form of leukemia recently, including the following:
- AbbVie (ABBV) and Pfizer (PFE) each got some drug approvals for flagship drugs to be used in older, frail patients who cannot handle intense chemotherapy (read more here)
- Daiichi Sankyo (OTCPK:DSKYF) had its new drug application accepted for quizartinib (read more here)
Now, you'll note that these are two very different areas of AML: treating the elderly and treating patients with a mutation in the FLT3 gene (re: quizartinib). Today's news is going to focus on Astellas' (OTCPK:ALPMY) (OTCPK:ALPMF) entry to the latter contest: gilteritinib. This FLT3 inhibitor has been making waves in the leukemia space, since it's the first of a new crop of "second-generation" inhibitors that was likely to see approval.
Of course, they weren't the first FLT3 inhibitor overall. That distinction goes to Novartis' (NVS) midostaurin (branded Rydapt). However, unlike other forms of leukemia with a targetable mutation (such as chronic myeloid leukemia, CML), targeting of FLT3 has not led to quite the same paradigm shift. One reason for that is that midostaurin is not the most potent FLT3 inhibitor, with relatively modest response rates.
Still, the approval of midostaurin last year was a good kick start to the era of precision therapy for AML.
The FDA has approved gilteritinib for the treatment of patients with relapsed or refractory AML that harbors a mutation in FLT3, as detected by an approved test (marketed by Invivoscribe). The approval was based on findings from an interim readout of the phase 3 ADMIRAL study, which demonstrated a 21% complete response rate in relapsed/refractory AML patients.
Furthermore, nearly one-third of the patients who were reliant on red blood cell transfusions were able to stop this procedure.
It's been a long time coming for being able to treat AML as a disease of various molecular subgroups. Since 2017, we've seen the first approvals for IDH-mutated, as well as FLT3-mutated AML. Gilteritinib holds significant promise, given its favorable response rate in the relapsed/refractory disease setting.
It's a bit of a shame that full results of the ADMIRAL study will not be presented at this year's ASH meeting. It would have been nice to be able to analyze these results and place them in the context of what we know about quizartinib, the drug most likely to be ALPMY's competition in the marketplace.
Now, ALPMY will turn its attention toward getting a full approval, with one randomized trial underway to make sure that gilteritinib is better than chemotherapy in the relapsed/refractory setting. There are also 3 other studies examining gilteritinib by itself after chemotherapy for FLT3-positive patients.
ALPMY is also conducting combination studies for gilteritinib, including with hypomethylating agents or with venetoclax (ABBV's drug) in FLT3-positive patients who cannot tolerate intensive chemotherapy. There's even a phase 1/2 study investigating gilteritinib along with Roche's (OTCQX:RHHBF) atezolizumab for relapsed/refractory disease.
Needless to say, this should be an interesting space to watch.
Key investment takeaways
For now, NVS's control of the FLT3-positive AML space is pretty safe, since it currently has the only approval for newly diagnosed disease. So if you're a holder of NVS, this news shouldn't impact on that.
Should you buy ALPMY? It, too, is a large pharma, and with FLT3-positive AML being a relatively small space (to say nothing about only patients with relapsed/refractory disease), the impact on its bottom line is not going to be momentous, overall. This is a bit of good news, and it should make you more confident if you're currently holding ALPMY stock. However, I don't think this alone should make you buy.
Overall, this is news worth paying attention to, but the true impact is going to come later as we get expanded approvals for the FLT3 inhibitors. Considering there are 19,500 new cases of AML per year in the US, and around 25% to 30% of these patients will be FLT3 positive, there are approximately 5,000 new patients each year who may benefit from these agents. With wholesale prices of midostaurin being approximately $15,000 per month, this means that these drugs have the potential to be a $900 million-per-year market at its upper limit.
That's something that is not worth ignoring, in my opinion.
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