(What follows is my analysis of the potential promises and pitfalls associated with the experimental MS drug ocrelizumab. For those who have not already done so, I urge you to read – or at least scan – the interview I conducted with Dr. Peter Chin, one of the pioneering researchers who worked on this drug. Dr. Chin is the Group Medical Director of Neuroscience at the pharmaceutical company that makes ocrelizumab, Genentech – click here for the interview)
Assessing the overall potential of ocrelizumab is more difficult than with most new drugs, as the therapy has a complicated history that must be considered when synthesizing informed views about it. Ocrelizumab, which will be marketed under the brand name Ocrevus, is a close sibling of the much older drug Rituxan (rituximab), whose mechanism of action ocrelizumab closely mirrors. Rituximab, which is manufactured by the same company that makes ocrelizumab, is already being used in many parts of the world as an effective MS therapy, even though it was never officially approved for this purpose. The reasons why ocrelizumab rather than rituximab was advanced in studies as an MS therapy are somewhat controversial; complicating matters further are ocrelizumab’s failure in trials for use in treating other autoimmune diseases (lupus and rheumatoid arthritis). Therefore, when attempting to make a sober assessment of ocrelizumab, one must look not only at the drug itself, but also at how it currently came to be on the verge of FDA approval.
First, let’s look at ocrelizumab itself, in terms of how the drug works and what recent clinical trials reveal about its effectiveness in the treatment of both relapsing and primary progressive multiple sclerosis.
Ocrelizumab is the first B cell therapy for MS proven to be effective in late stage clinical trials. In very simplistic terms, the human immune system is comprised chiefly of 2 types of cells, T cells and B cells, which each use different mechanisms to attack and kill invading bacteria or viruses. Until very recently, the vast majority of MS researchers, who see MS as an autoimmune disease in which the immune system turns against the body’s own cells, considered the multiple sclerosis disease process to be driven almost exclusively by T cells. MS drugs such as Tysabri and Gilenya were designed to specifically target these cells. B cells were given short shrift, and were largely dismissed as having no real relevance in the MS disease process.
The success of ocrelizumab – a drug which destroys B cells – in treating MS has upended these prior assumptions and has forced researchers to rethink their multiple sclerosis disease models. In clinical trials, ocrelizumab, an intravenous drug administered approximately every 6 months, proved to be remarkably effective in treating relapsing multiple sclerosis, and even had a modest effect on PPMS. Let’s look at the actual trial results.
Two separate trials were conducted testing ocrelizumab against the interferon drug Rebif in patients with relapsing multiple sclerosis. These two trials were called OPERA 1 and OPERA 2 (click here). Both two-year trials involved one group of patients taking ocrelizumab and another taking the interferon drug Rebif, and comparisons were made as to the overall effectiveness of ocrelizumab versus the interferon drug. The results were very impressive. Compared to the Rebif treated patients, the ocrelizumab trial subjects experienced a reduction in relapse rates of 46% and 47% in the two trials. Additionally, there was a 40% reduction in confirmed disability progression and a 95% reduction in new enhancing lesions. These results rival or surpass any of the other MS drugs currently on the market. There were no significant differences in the number of adverse events (bad side effects) between the ocrelizumab and Rebif treated patient populations in the relapsing multiple sclerosis trials.
The ocrelizumab PPMS trial was named ORATORIO (click here). This trial lasted 2 ½ years, and randomly assigned 732 patients in a 2 to 1 ratio to receive either ocrelizumab or a placebo. In other words, twice as many trial subjects received ocrelizumab than received placebo. The highlight of this study was that the ocrelizumab treated patients experienced a 25% reduction in time to progression when compared to their placebo-controlled counterparts. Specifically, 29.6% of ocrelizumab treated patients and 35.7% of placebo treated patients experienced a measure of disability progression over the course of the study. This is the first time in a placebo-controlled scientific trial that any multiple sclerosis drug has displayed effectiveness in slowing down the progression of disability in Primary Progressive patients. Ocrelizumab also displayed efficacy over placebo in a number of other outcome measures as well, including the timed 25 foot walk.
As I discussed with Dr. Chin during our interview, it’s important to understand that ocrelizumab did not reverse or even stop the progression of disability in trial subjects. It slowed progression by about 25%. What does this mean for patients in a real-world setting? Well, speaking strictly in a broadly hypothetical basis, if an individual PPMS patient left untreated might need a cane four years after diagnosis, that same patient, if responsive to ocrelizumab, might not need a cane for five years. Again, this is strictly a hypothetical case; PPMS effects patients in widely varying degrees of severity. Additionally, the ORATORIO trial only lasted 2 and half years. How the drug's effectiveness manifests over longer periods of time is not yet understood.
Unlike the relapsing multiple sclerosis ocrelizumab trials, the PPMS trial did reveal some potentially troubling adverse events. Opportunistic infections (mostly respiratory infections and oral herpes) were more common in ocrelizumab than placebo, and the rate of cancer in ocrelizumab treated patients was approximately 3 times that found in placebo treated patients, 2.3% versus 0.8%. Though Genentech says that no direct causal relationship between the cancers in ocrelizumab treated patients could be established, the fact that slightly more than 1 in 50 trial subjects on the drug developed cancer is sure to raise eyebrows, but since similar cancer rates were not seen in the relapsing multiple sclerosis trials these numbers are surely open to question.
There are also some concerns regarding the design ORATORIO study. Back in the mid-2000’s, Genentech conducted a PPMS trial using rituximab, which at first was deemed a failure. Later review of the trial data revealed, though, that a subset of PPMS patients did appear to gain benefit from rituximab therapy (click here). These patients were generally younger than 50 years old, were less disabled, and had enhancing lesions on their MRIs. It’s generally thought that patients fitting this description account for between 10%-15% of the overall PPMS population. The ocrelizumab PPMS trial, though, included about 26% of patients fitting this profile, or approximately double that seen among real-life PPMSer’s. This means that the ORATORIO trial was heavily weighted with patients who were likely to respond to ocrelizumab, since the drug acts in much the same way as rituximab. The ocrelizumab PPMS trial was not designed to discern differences in the effectiveness of the drug between patients with enhancing lesions and those without, but Genentech says there was a “directional consistency” to the trial results, suggesting that the drug was effective in all patient subgroups to one degree or another. Still, the fact that the trial was frontloaded with likely responders is another eyebrow raiser, and may be something that the FDA looks at when making its approval decisions.
Okay, now that we’ve looked at the ocrelizumab MS trials themselves, let’s dive into the history of the drug. Back in the early 2000’s, some MS researchers began investigating whether therapies that destroy B cells might be effective in treating MS. As mentioned earlier, at the time this with a rather radical idea. The drug that was chosen for study was Rituxan (whose generic name is rituximab – click here), a drug developed by Genentech years earlier that had been approved in 1997 for use in fighting non-Hodgkin’s lymphoma and certain types of leukemia. Rituximab, like ocrelizumab, works by zeroing in on a protein found on most types of B cells, called CD20, and then killing the cells on which this protein is located. Though both drugs target and kill B cells, they do so in slightly different ways, and these differences may result in variances in safety and efficacy. Think of the drugs as two hitmen; one likes to slit his victims throats, the other prefers to strangle them. Both get the job done, but their differing killing techniques might effect witnesses differently. In the case of ocrelizumab and rituximab, these differences may effect the actions of other immune cells, thus accounting for possible differences in the safety and efficacy of the drugs.
In the mid-2000’s, MS researchers put rituximab to the test by using it in “proof of concept” trials in patients with RRMS and PPMS. When the trial results were revealed in 2008, the drug proved itself to be extremely effective in treating relapsing remitting MS, but not effective in treating PPMS (click here and here). It’s important to note that the RRMS trials were small, early stage trials, but the PPMS trial was larger and later stage. As mentioned earlier, later parsing of the PPMS data did reveal a subgroup of patients on whom the drug appeared to have some positive effect.
Given the success of the rituximab RRMS trials, the fact that a subset of the PPMS trial population appeared to benefit from the drug, and rituximab’s long history as a successful oncology drug, it’s reasonable to assume that the drug would have been greenlighted for further development as an MS treatment. Instead, all development of rituximab as an MS treatment was halted, and the focus shifted instead to ocrelizumab, a new experimental Genentech product that also targeted B cells via the CD20 protein. While there is some perfectly valid scientific rationale for this choice, many facts and circumstances point to financial motivations playing an oversized role in the decision to advance ocrelizumab rather than rituximab as a potential treatment for MS.
The scientific rationale for choosing to proceed with ocrelizumab is that the drug is comprised primarily of human proteins (the drug is a “humanized” monoclonal antibody), while rituximab contains a mix of mouse and human proteins (making it a “chimeric” monoclonal antibody, meaning that it contains proteins from more than one species). Theoretically, a humanized molecule should be better tolerated by patients than a chimeric drug, especially when used for treating chronic diseases which require continued administrations of the drug. That said, rituximab did have a very good safety profile in its role as an oncology drug, and very few adverse effects were seen in the early rituximab MS trials.
Genentech’s financial motivations for switching from rituximab to ocrelizumab were many. First and foremost was the fact that rituximab was due to come off patent in 2015, meaning that other drugmakers would be free to come in and market their own versions of the drug at that time. As ocrelizumab is a brand-new product, Genentech will have exclusive rights on it for decades to come. In addition, several corporate partnerships were also at play which made ocrelizumab the preferred candidate for further development. Here’s an explanation of the situation, from an article that appeared on the biotech industry news site Genetic Engineering and Biotechnology News in 2010 (click here). Keep in mind that Roche is the parent company of Genentech:
“The operating profits for Rituxan are currently split 60–40 between Roche and Biogen Idec, respectively. But profits for Ocrelizumab would be split 70–30 in Genentech's favor, accounting for Genentech’s enthusiasm to move ahead with the development of Ocrelizumab in MS, at the expense of Rituxan, which loses patent protection in 2015.”
Of course, there is no direct proof that the switch from Rituxan to ocrelizumab was driven primarily by financial considerations (except, perhaps, in files tucked away in the executive offices at Genentech), but I’ve learned through my years researching and writing about these topics that one can never be too jaded in assessing the motivations of the upper echelon decision-makers of Big Pharma. These are publicly traded companies whose officers are, by law, mandated to be beholden to their shareholders, not to the patients taking their products. Welcome to the realities of the medical industrial complex, in which diseases have been transformed into multibillion-dollar a year industries.
Whatever the circumstances, plans for further studies into the use of rituximab in treating MS were abandoned, and early trials using ocrelizumab to treat MS were initiated. In addition to the MS trials, ocrelizumab trials were also started on patients with rheumatoid arthritis (RA) and lupus erythematosus (LE). It’s interesting to note that rituximab was approved for use in treating rheumatoid arthritis in 2007, and has been used effectively and safely in that role since then (click here).
Genentech’s grand plans for ocrelizumab were almost completely disrupted in 2010, when the trials in RA and lupus were halted due to patient deaths and the occurrence of opportunistic infections (click here ). In the parlance of medical research, the risk versus benefit analysis in these trials did not warrant further study. In the parlance of everyday people, dead patients suck. It should be noted that patients in the ocrelizumab rheumatoid arthritis trial were also taking other immunosuppressive drugs, but then again so are most of the patients who have been using rituximab to treat their RA since its approval in 2007.
Ocrelizumab studies in MS were continued because these disastrous infections and patient deaths were not seen in early ocrelizumab MS trials, and also because it’s generally assumed that MS patients and their doctors have a higher tolerance for risk due to the potentially catastrophic nature of the disease (click here). This assumption is borne out by the MS community’s acceptance of drugs like Tysabri, which has a proven link to the deadly brain infection PML. Hundreds of MS patients have contracted this infection due to their taking Tysabri. Other MS drugs, such as Gilenya and Tecfidera, have also been linked to opportunistic infections such as PML. MS certainly isn’t a disease for the faint of heart.
In the years since the rituximab MS studies were shelved by Genentech, MS neurologists have been using the drug on an “off label” basis due to the obvious potential of the drug displayed in those early trials. “Off label” refers to the fact that doctors are free to prescribe any FDA approved drug for any indication whatsoever, even if the drug has not been approved for that purpose (click here). Many MS neurologists here in the USA as well as in Europe have been using rituximab to treat MS patients safely and effectively for years. The use of rituximab in MS is especially prevalent in Sweden, and a recent study out of that country that took a retrospective look at MS patients treated with rituximab found that the drug was startlingly effective and had an excellent safety profile (click here). As noted earlier, rituximab has also proven safe and effective in treating rheumatoid arthritis. Remember, the RA trials for ocrelizumab had to be halted due to opportunistic infections and patient deaths.
It should be noted that over its 20-year history rituximab has been linked to some cases of PML, but to a far lesser degree than drugs like Tysabri. In rheumatoid arthritis patients, it appears the rate of PML in Rituxan treated patients is on the order of 1 in 25,000 (click here). Rituximab has also been linked to other opportunistic infections, but again, at a lower rate than is seen in most other MS drugs. Let’s face it, any drug that profoundly changes the highly evolved human immune system is bound to open patients up to infections they wouldn’t otherwise contract. Ocrelizumab and rituximab both destroy B cells, one of the major components of the human immune system. No one knows what the long-term effects of living without any B cells might be. We do know, though, that the long-term effects of living with MS can be harrowing. Such is the state of the current MS treatment paradigm.
In conclusion, while the excitement generated by the impending approval of ocrelizumab for relapsing multiple sclerosis and primary progressive multiple sclerosis is certainly warranted, expectations, especially for those with PPMS, should be kept realistic. Ocrelizumab will likely slow the rate of disability progression for some progressive MS patients, and even though this isn’t the revolutionary change patients battling PPMS are so fervently hoping for, it is a start. Relapsing multiple sclerosis patients can expect ocrelizumab to be among the most effective disease modifying drugs on the market.
The fact that rituximab, a very similar drug with a proven record of efficacy and safety, is an available and very viable option should play into treatment decisions, as should the failed ocrelizumab trials in RA and lupus, and the increased cancer rates seen in the ocrelizumab PPMS trials (again, these rates could be aberrations). These factors need not make patients shy away from ocrelizumab, but there is every reason to explore them with your neurologist. Don’t be afraid to ask your doctor why they might favor one drug over another. This holds true when deciding on any MS treatment. Remember, the doctor-patient relationship should never be a dictatorship, but a partnership. Here’s to hoping that ocrelizumab proves itself worthy of the buzz it’s generated in advance of its anticipated FDA approval.
And here’s to more desperate hoping that MS researchers soon come up with methods other than profoundly kneecapping the human immune system in their search for ways to treat MS.