Finally, after a week or more of thinking and contemplation my opinion about the ofatumumab vs. teriflunomide trial data (ASCLEPIOS I and II); another of my ECTRIMS highlights.
The result of the ASCLEPIOS I and II are not unexpected and in line with the treatment effects of anti-CD20 therapies with some caveats.
- Both ASCLEPIOS I and II studies met their primary endpoints in patients with relapsing forms of MS (RMS); overall ofatumumab (OMB157), a subcutaneous, potent, fully-human antibody targeting CD20 positive B-cells, delivered efficacy with a favorable safety profile
- RMS patients on ofatumumab had a reduction in annualized relapse rate (ARR) by 50.5% (0.11 vs. 0.22) and 58.5% (0.10 vs. 0.25) compared to Aubagio®* (teriflunomide) (both studies p<0.001) in ASCLEPIOS I and II studies respectively
- Ofatumumab showed highly significant suppression of gadolinium (Gd) T1 lesions when compared to Aubagio®, demonstrating a profound suppression of new inflammatory activity
- Ofatumumab showed a relative risk reduction of 34.4% in 3-month confirmed disability progression (CDP†) (p=0.002) and 32.5% in 6-month CDP (p=0.012) versus Aubagio® in pre-specified pooled analyses
- Ofatumumab, if approved, will potentially become a treatment for a broad RMS population and the first B-cell therapy
Inflammation: relapse rate, focal MRI activity (Gd-enhancing & new T2 lesions) and neurofilament data.
I have made the point that these three markers measure focal inflammation, driven by adaptive immunity, and there is little doubt that ofatumumab is superior in suppressing inflammation compared to teriflunomide. Does this make ofatumumab superior to other very high efficacy DMTs, such as natalizumab, rituximab, ocrelizumab, alemtuzumab and HSCT? I suspect not. To prove this we would need head-2-head studies. I also think there are floor effects on these outcomes, i.e. you can only reduce relapse rates to around 0.1 to 0.2 and no lower. Why? I suspect some relapses are pseudo-relapses and are due to intermittent symptoms in relation to infections, fatigue and possibly hidden symptoms.
Please note that I don’t consider peripheral blood neurofilament levels (pbNFL) to be a neurodegenerative marker in the context of MS. All the data I have seen to date indicates that it is linked to focal inflammatory activity. Clearly more needs to be done in progressive MS with pbNFL to understand what it means in inactive or smouldering MS.
End-organ damage: disability progression and brain volume data
I was disappointed with how ofatumumab did against teriflunomide in delaying disability progression and reducing the relative loss of brain volume. This will be ofatumumab’s Achille’s heel. Why? It is clear that MS the disease is not focal inflammation; I have made the point that based on the Prentice criteria, both relapse and focal MRI activity don’t predict disability outcomes in natural history studies and placebo arms of clinical trials. If focal inflammation was MS then relapses and focal MRI activity would predict outcome whether or not you are on a DMT. The point I making here may be a philosophical one, but it a very important one.
In comparison, sustained or confirmed disability progression has to be MS and is based on the pathological correlates that define MS (demyelination, neuroaxonal loss and gliosis).
Why did ofatumumab do so poorly on these metrics relative to teriflunomide? It could be that teriflunomide is the outlier and this opinion is based on several observations.
- Teriflunomide is the only DMT to have a consistent effect on disability progression; i.e. both teriflunomide phase 3 placebo-controlled trials were positive on this outcome. In addition, the treatment effect or impact of teriflunomide on disability progression has always been greater than what you would expect from its impact on relapses. For the tuned-on readers, you would have noticed the same disconnect between relapses and disease progression was observed in the ponesimod vs. teriflunomide trial.
- Teriflunomide also has a significant effect on brain volume loss compared to placebo, which again is out of proportion to its impact on relapses (see picture below).
- Teriflunomide is more effective when used 2nd and 3rd line. Teri is the only DMT to show the latter and this observation was seen in both phase 3 studies, which makes it likely to be a real, and a very important, finding.
- Teriflunomide is a broad-spectrum antiviral agent, which may be part of its mode of action in MS. Could teriflunomide be targeting the viral cause of MS independent of its effects on the immune system’s response to that virus? This needs more study, but teriflunomide is the outlier, or exception, that disproves the dogma.
Is ofatumumab being underdosed?
Ofatumumab is being given at a dose of 20mg subcutaneously monthly. This dose was chosen to keep B-cells depleted, but not severely depleted, so as to allow rapid repopulation of peripheral B-cells numbers if ofatumumab is stopped. In other words, B-cell depletion is relatively mild compared to ocrelizumab 600mg every 6 months. With ocrelizumab, it takes 6 months or longer to start to see B-cell reconstitution.
I don’t buy this argument. The repopulation kinetics with ofatumumab are based on relatively short-term dosing studies in which deep tissue and in bone marrow B-cell depletion is likely to be relatively modest. I suspect with long-term dosing with ofatumumab deep tissue and bone marrow B-cell depletion is more likely and hence the B-cell repopulation kinetics will mimic that of rituximab and ocrelizumab.
I also think rapid B-cell repopulation is likely not to be relevant as the new B-cells will almost certainly be bone marrow-derived naive B-cells and not memory B-cells.
The question I have is the 20mg per month of ofatumumab sufficient to penetrate the CNS and clear the intrathecal of CNS resident B-cell follicles?
At the AAN this year Stephen Hauser presented data indicating that when it comes to disability progression, not relapse rate or MRI activity, the extent of exposure to ocrelizumab is very important.
The greater the ocrelizumab exposure the more effective it was at delaying disability progression. This could be related to deep tissue (peripheral) and end-organ (central) B-cell depletion. There is mounting evidence that the B-cells and plasma cells within the brain and spinal cord of MSers are driving some of the slow-burn we see clinically and on MRI (smouldering MS). What I am saying is that ocrelizumab could be superior to ofatumumab when it comes to scrubbing the brain clean of pathogenic B-cell follicles. Therefore it more important than ever to test this hypothesis in a head-2-head study of ocrelizumab vs. ofatumumab (OVO study) or the DODO study comparing double-dose (1200 mg) vs standard-dose (600 mg) ocrelizumab (DODO study) to see if the higher dose of ocrelizumab has a bigger impact on the intrathecal B cell response than the standard dose.
I would suggest these studies include next-generation MRI and other biomarkers to test the CNS penetration hypothesis. If these studies are positive, i.e. ocrelizumab is superior to ofatumumab and double-dose ocrelizumab is superior to single-dose ocrelizumab, it will not only tell us a lot about how anti-CD20 therapies work in MS, but it may answer the question of whether or not we need to target the intrathecal or CNS B-cell response in MS. The latter hypothesis is being tested by our group in two studies at present. We would love to add a third and fourth study to the portfolio. If you work for Novartis or Roche please tell the powers that we are really, really, interested in doing both the OVO and the DODO studies.
What about teriflunomide?
Don’t forget that the implications from the ponesimod vs. teriflunomide and ofatumumab vs. teriflunomide trials are quite profound. Teriflunomide is quite a remarkable DMT and we need to explore its antiviral effects in MS in more detail and understand what it is doing in MS independent of its rather weak anti-inflammatory effects. This is why I have proposed using teriflunomide as a maintenance therapy post-induction. In my ECTRIMS hot topic presentation, I called the trial the iTeri study (see slide show above).
If you work for Genzyme-Sanofi please tell the powers that be that we are really, really, interested in an induction-maintenance trial with both teriflunomide (iTeri study) and a second with your BTK inhibitor (iBruT study).