Asterias interview: stem cell spinal cord injury trials advance

Recently I had the opportunity to talk with the leadership of Asterias, a California biotech doing exciting clinical research using stem cells as the basis for treatment of spinal cord injury. The interview covers the past (Geron patients), present, and future. I spoke with Asterias President and CEO Stephen Cartt and CMO Edward Wirth.

How are the Geron patients doing?

Asterias: They are doing well. We have to remember that they got the low dose (2 million OPC1 cells) and we estimated that an efficacy dose was more like 10-20 million cells. The good news is that the safety profile is very strong. The trial has 15 years follow up including 5 years of MRIs and then phone follow up. There is so far sustained evidence of prevention of cavity formation in 4 out of 5 patients, which suggests durable engraftment. Out to 1 year no evidence of an antibody or T cell response to OPC1 cells. We will look at that out to 5 years. No masses or tumors or health issues attributable to cells. We are very excited by those safety data, which were also submitted to the FDA.

Dr. Richard G. Fessler, professor of neurological surgery at Rush University Medical Center in Chicago, is shown here making final preparations to inject 10 million AST-OPC1 cells into a spinal cord injury patient in August 2016. Dr. Fessler is the lead investigator of the SciSTAR study looking into AST-OPC1 as a treatment for spinal cord injury.

Are AST-OPC1 heterogeneous?

Asterias: The overwhelming percentage of cells are OPCs. In the spirit of full disclosure there are some other characterized cell types in the mix too. We are working to more fully characterize those cells. In the old days a lot of characterization was done by immunostaining. Now we are doing RNA-Seq and other more up to date studies. An interesting question is: do any of the other minor players (cell types) contribute?

What happens with the AST-OPC1 prior to Day 0? Is it a thaw-and-go kind of situation or do the cells get cultured for a while?

Asterias: The cells are thawed and washed (to remove cryopreservative) on the day of surgery. This takes 2-3 hours and is typically done in the morning. STAT gram stain is also done and once they pass, they are then released to the OR for injection. Another sample is sent for 14-day sterility test. So there is no expansion of the cells prior to injection, just washing and resuspension into the injection medium. We find there’s about 80% viability.


Can you update us on the spinal cord injury trial? How do we tell the difference between a therapeutic effect and spontaneous recovery?

Asterias: So this is something that has been investigated in detail by the SCOPE (spinal cord outcomes partnership endeavor) group with Dr. John Steeves Professor at UBC and Andy Blight, the Acorda therapeutics CSO. There have been some papers published. What is the SCI rate of recovery with standard of care? The majority of patients with an American Spinal Injury Associate (ASIA) Impairment Scale Grade A injury (known as an AIS A injury) will recover 1 motor level on one side of the body. Very few of these patients spontaneously recovery 2 motor levels, even over the longer term. With OPC1, our goal is 40-50% of patients having >= 2 motor levels on one side of body, which is well beyond typical spontaneous recovery, and so far by day 90 some of our patients in the 10 million cell cohort had already recovered 2 motor levels (that was our 6 month target). We haven’t tested the 20 million dose yet, but believe there’s potential for further improvements with this higher dose. The dose response related to motor score is encouraging so far with respect to the 2 million and 10 million cell doses.

Can you tell me more about the complete thoracic versus subacute cervical trials? What are the differences in the patients for instance?

Both studies tested patients with severe impairment. The thoracic study and the first three cohorts of the cervical study were in patients with AIS A injuries, which is complete loss of motor and sensory function below the site of injury. We also recently got permission to expand the study to two additional cohorts of patients with AIS B injuries. These patients have complete loss of all motor function but some preserved sensory function below the level of their injury.

Both studies are similar.

One difference between the original thoracic and the current cervical study is timing of delivery of OPC1. In the original study in thoracic injuries, Geron injected OPC1 within 7-14 days of injury; in the ongoing Asterias cervical study, there is a 14-30 days post-injury window. 14 days is extremely tight, while 14-30 is more feasible. Most of the patients got it close to the 30-day cutoff. The reason scientifically we are focusing on the subacute window is that there is a sense we will obtain better engraftment in that period. We want to avoid the early inflammation and the scar tissue formation period (begins ~3 months). We could push the window out a few more weeks. The rationale for also going into cervical is that if you can mediate anatomical repair, via OPC stimulating endogenous repair, collectively over several segments, if that can mediate functional repair, it can have a huge impact on a person’s quality of life.

Any hope for lower extremity function restoration?

Asterias: It’s a tall order for the severe injury cases such as patients with AIS A injuries. In these patients we believe improvements in upper extremity function are far more feasible. In less severe, AIS C injuries (in which some level of both sensory and motor function are preserved below the level of the injury), there may be a good chance for some leg motor function recovery.

Any side effects including of immunosuppression?

Asterias: There have been no clear negative effects of immunosuppression. Going into the study the primary concern regarding immunosuppression was could infections be more frequent or worse? We tried to limit the immunosuppression to low dose and short term in order to minimize this risk. So far in the study we haven’t seen any evidence of increased infections, which is encouraging.

What about company policy regarding trial participants and the media? We’ve seen at least one patient talking to the media.

Asterias: Several of our patients have chosen to make public statements regarding their participation in our study. This is their choice to make. So much has been taken away from their lives. They’ve seen benefit so understandably they like the idea of expressing what they’ve experienced and they want to educate other patients. Their doctors communicated to us that the patient is interested in talking. There are HIPPAA considerations.

What are your future plans and do they include RCTs?

Asterias: The logical next phase is a randomized controlled trial. We’re currently enrolling in our single arm, open label trial for the AIS A 20 million cell dose cohort and the AIS B 10 million cell cohort (and later 20 million). That is expected to wrap up Q3-4 next year. As the data come in, we can make plans.

The next big readout is January of 2017 when we should have cumulative 6-month data for the AIS A patients at 10 million cells. 5 patients.
As this and other data from the subsequent cohorts become available, we’ll examine data, talk with investigators, the FDA, etc. to determine our plans for subsequent trials.

Do you have any non-SCI-related work in the pipeline?

Asterias: OPC1 could be helpful for other indications. We have done some preclinical work related to MS and certain kinds of stroke, which have been encouraging. Some pediatric conditions. Overall, we want to get that first clinical win before we pursue other areas.

Disclosure: I have no financial ties to Asterias.