MRK - Aptose: High Risk High Reward. Watch Its Phase I Studies

• Aptose's second quarter update was undramatic, with management indicating that they've fully enrolled their Phase I luxeptinib studies at 750mg and are moving on to 900mg.
• Dose escalation awaits in the APTO-253 AML/MDS study, but management is also going to start enrolling patients with certain eligible B-cell cancers.
• Management continues to see dose-related reductions in lesion size and blast reductions, as well as reversal of aggressive disease, but there haven't been any additional confirmed responses.
• I still see meaningful upside potential in Aptose shares, but I don't see a clear path to that upside without some substantial positive clinical news, confirmed clinical responses in particular.

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