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Expert Interview

Slingshot members are talking to an expert! The topic is:

Discussing the latest GBT Sickle Cell Trial for Voxelotor (Previously GBT440) and its market potential

Ticker(s): GBT, BLUE

Who's the expert?

Name: Dr Cage Johnson - MD

Institution: University of Southern California

  • Among the world’s leading authorities on sickle cell disease; former Director of the Sickle Cell Center at Los Angeles County and USC Medical Center and Professor Emeritus of Medicine & of Physiology & Biophysics.
  • Currently manages 125 patients with sickle cell disease.
  • Has published nearly 100 papers on sickle cell disease and other hemoglobinopathies in peer reviewed journals and has presented with the National Institutes of Health, the National Science Foundation, the Food and Drug Administration and the Sickle Cell Foundation.

Interview Questions

Please describe your background and experience with Sickle Cell Disease.

Added By: joe_mccann

What is the typical treatment regimen of your current patient population? Assuming Voxelotor is approved how likely will the prescribing community switch to Voxelotor or will there be a gradual shift as consensus builds for the products use?

Added By: joe_mccann

What are the most important endpoints for a drug in Sickle Cell to show an efficacy impact on? Is the HOPE study's primary endpoint of Proportion of participants with increase in Hb >1 g/dL from Baseline to Week 24 the best? Is there another endpoint such as days in hospital during an acute attack, opioid consumption, PRO scores more relevant?

Added By: joe_mccann

What is your high level view of the mechanism of action and approach for Voxelotor?

Added By: joe_mccann

The Phase1/2 study showed that 46% of patients in the treatment group demonstrated an increase in hemoglobin (greater than 1 g/dL increase). How meaningful are these results for you?

Added By: joe_mccann

On a scale of 1-10 how excited about this program are you for patients and scientifically?

Added By: joe_mccann

I realize you are on the DSMB for the HOPE trial. With this in mind, and without sharing any non-public information, what kind of symptoms would you have to have seen with regards to safety, to have ended the trial early or have had it enter a clinical hold?

Added By: user3fxk89p

What do you think needs to be demonstrated for approval of the drug? Keeping in mind the primary endpoint is Hb increase of >1g/dL, secondary of VOC and PRO outcomes.

Added By: user3fxk89p

What is your opinion on the PRO? Do you think it will be effective and show statistical significance between placebo and the drug arms?

Added By: user3fxk89p

Do you think the trial is sufficiently powered to show statistical significance on VOCs? Is it enough to show trend?

Added By: user3fxk89p

In a trial where many patients have long history of VOC and organ damage caused by chronic disease, is it realistic to expect that Voxelator could result in (1) rapid decrease in fatigue and or (b) rapid decrease in pain?  Is it possible that we could see a rapid decrease in  fatigue to to higher blood oxygenation but not a rapid decrease in pain since these patients have L-T organ damage that may not be reversed 

Added By: aklapholz

In the event that the Hope trial shows significant clinical efficacy (reductions in VOC and SCD exacerbations of 60-80% plus significant improvement in fatigue and pain), with only minor safety / tolerability concerns, what proportion of SCD patients wouldn't want or need voxelotor (i.e. because they are asymptomatic or SCD is not affecting them)?  

Added By: userbdcc81a6

What is your opinion on the theoretical safety risk including ischemia, stroke, peripheral hypoxia, and off-target aldehyde mediated binding to protein N-termini? Do you think the risk is more prominent in patients treated with hydroxyurea due to higher O2 affinity of HbF?

Added By: user3fxk89p

Is hydoxyurea considered the SOC at this point (post BABY HUG, and lack of DNA damage seen in HUSTLE)? If so, are there ethical considerations to having PBO as the control arm instead of hydroxyurea as control. Would you prefer Tx arm to be hydroxyurea + GBT's Voxelotor  and comparison arm to be hydroxyurea? 

Added By: william gerber

Given that Voxelotor HOPE trial does not include hydroxyurea, but allows use of hydroxyurea, do you see potential for unbalanced use as a potential confounder?

Added By: william gerber

What are the non-Tx factors that can cause Hb levels to vary?  How variable have the Hb levels been of your patients for reasons other than treatments (e.g. time of day, hydration, nutrition, exercise, altitude, smoking, vitamin supplementation, etc).  If Hb levels are variable for non-treatment reasons, would you expect this to be a reliable trial endpoint?

Added By: william gerber

Would your patients would have appreciated the PRO program for scoring their symptoms.  Do you see this as a necessary improvement over past measures, such as VOCs, days in hospital, etc.

Added By: william gerber

Does background hydroxyurea affect the efficacy of other simultaneous treatments? Since the trial is not stratified for hydroxyurea or baseline characteristics, what likelihood do you see that some baseline bias could affect the trial outcome?

Added By: user3fxk89p

What is your opinion on other treatments in clinical trials for SCD? Specifically selectin-class and bluebird bio's gene-related approaches?

Added By: user3fxk89p

Assuming selectin's and bluebird bio's drugs approved along with Voxelotor, when would you expect to use each treatment?

Added By: user3fxk89p

To what extent is voxelotor's market potential limited by gene therapy approaches to SCD? 

Added By: usera453b44a

How long would a patient take Voxelotor before you would consider it a safe drug to take indefinitely?  Do you safety concerns about this drug?

Added By: william gerber

What is your background? What kind of patients do you treat and what kind of treatment paradigms are normal for both adolescent and adult patients?

Added By: user3fxk89p

What is your opinion of Endari or L-Glutamine as a therapy for SCD?

Added By: user3fxk89p

How familiar are you with Voxelotor? What is your opinion of it considering all of the publicly known data?

Added By: user3fxk89p

What is your opinion on the 1500 mg dose which has not yet been tested? Does it present additional safety risk? Do you expect increased efficacy?

Added By: user3fxk89p

What would you say is the probability of success of HOPE Part A? Total Trial? What are you looking for in the Part A readout?

Added By: user3fxk89p

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