BioMarin Release: Bay Area Biotech Solidifies Status as Top Dog in Hemophilia A Gene Therapy

For the six patients at the high dose and previously on a Factor VIII prophylactic regimen, the mean annualized bleeding rate dropped 91% from 16.3 before the BMN 270 infusion to 1.5 two weeks after being dosed (median annualized bleeding rate dropped from 16.5 to 0).  For those same six patients, the mean annualized Factor VIII infusions fell 98% from 136.7 to 2.9 (median annualized Factor VIII infusions fell from 138.5 to 0). (See Table 3)

Since the last update, six of the seven patients at the high dose as of the most recent reading are within the normal alanine aminotransferase (ALT) range, and one patient is less than 5% above the upper limit of normal, which is 43 U/L for the central laboratory in this study.  (See Table 4)  Patients successfully tapered off of steroids with no lasting significant impact on Factor VIII expression or ALT levels.  The requirement for prophylactic corticosteroids has been removed for all newly enrolled patients in this study. 

Study medication was generally well tolerated.  No serious adverse events were observed, and most common adverse events were mild in severity. 

The next steps for the program are to begin a potentially registration enabling Phase 2b study in 3Q 2017.  In addition, the company is expected to commission its commercial gene therapy manufacturing facility by mid-2017.

"These data continue to show promising evidence that restoration of clotting function can be achieved by gene therapy," said John Pasi, Ph.D. F.R.C.P, Professor of Haemostasis and Thrombosis at Barts and the London School of Medicine and Dentistry and primary investigator for the BMN 270 Phase 1/2 clinical trial.  "The increase in Factor VIII levels we have seen has the potential to stop patients bleeding and has changed how we think about treating hemophilia. For the first time we can truly start considering the opportunity for our patients to live a more normal life."

"We are proud that we have been successful in establishing a leadership position in gene therapy for the most common form of hemophilia, and we are intent on initiating potentially registration enabling trials to provide patients with a new treatment option," said Hank Fuchs, M.D., President, Worldwide Research & Development at BioMarin.  "To see data that shows a 91 percent drop in the mean annualized bleeding rate and a 98 percent drop in prophylactic infusions coupled with mean and median Factor VIII expression levels in the normal range opens up an exciting treatment possibility for hemophilia A patients."

Table 1:  Factor VIII Levels (%) of High Dose Patients* by Visit (N=7)

*All patients had severe hemophilia A defined as equal to or less than 1% of blood clotting factor.

**Weeks were windowed by +/- 2 weeks

***For week 32, one patient had no Factor VIII reading, for week 40, one patient had not reached week 40 and for week 44, only 2 patients reached a week 44 reading

****Bolded numbers are in normal range of Factor VIII as defined by the World Federation of Hemophilia, http://www.wfh.org/en/page.aspx?pid=643 (link current as of Jan. 8, 2017). Factor VIII levels are determined by one-stage assay.

Table 2:  Summary of Factor VIII Level (%) of High Dose Patients at Most Recent Evaluation (N=7)

Table 3:  Summary of Annualized Bleeding Rate (ABR) and FVIII Infusions of High Dose Patients Previously on Prophylaxis (N=6)

* Rates were based on data from week 3 after BMN270 infusion through last follow-up visit

**Obtained from medical records.

***5 of 6 patients had 0 bleeds requiring Factor VIII infusions and 0 Factor VIII infusions from Week 3 after BMN 270 infusion.

Table 4:  Summary of ALT Levels in High Dose Patients at Most Recent Evaluation (N=7)

All patients currently off steroids.

Phase 1/2 Study Design

The current Phase 1/2 study is evaluating the safety and efficacy of BMN 270 gene therapy in up to 15 patients with severe hemophilia A defined as less than or equal to 1% of blood clotting factor. The primary endpoints are to assess the safety of a single intravenous administration of a recombinant AAV vector coding for human-coagulation factor VIII and to determine the change from baseline of factor VIII expression level at 16 weeks after infusion. The kinetics, duration and magnitude of AAV-mediated factor VIII activity in individuals with hemophilia A will be determined and correlated to an appropriate BMN 270 dose.

This is a dose escalation study with the goal of observing an increase in factor VIII levels. Secondary endpoints include assessing the impact of BMN 270 on the frequency of factor VIII replacement therapy, the number of bleeding episodes requiring treatment and any potential immune responses. Patients will be monitored for safety and durability of effect for five years.

About Hemophilia A

Hemophilia A, also called factor VIII (FVIII) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII, a clotting protein. Although it is passed down from parents to children, about 1/3 of cases are caused by a spontaneous mutation, a new mutation that was not inherited.[1] As an X-linked disorder, hemophilia A mostly affects males, occurring in approximately 1 in 5,000 male births.[2] People living with the disease are not able to form blood clots efficiently and are at risk for excessive bleeding from modest injuries, potentially endangering their life. People with severe hemophilia often bleed spontaneously into their muscles or joints. The standard of care for the 43% of hemophilia A patients who are severely affected, is a prophylactic regimen of factor VIII infusions three times per week.[3] Even with prophylactic regimens, many patients still experience microbleeds and spontaneous bleeding events that result in progressive joint damage.

Table 5:  Severity of Hemophilia*

*Information sourced from World Federation of Hemophilia, http://www.wfh.org/en/page.aspx?pid=643 (link current as of Jan. 8, 2017)

**Percentage calculated based on the number of international units (IU) per milliliter (ml) of whole blood.

***Severity describes how serious a problem is. The level of severity depends on the amount of clotting factor that is missing from a person's blood. 

About Gene Therapy

Gene therapy is a treatment designed to alter a genetic problem by adding a corrected copy of the defective gene. The functional gene is inserted into a vector – containing a DNA sequence coding for a specific protein – that acts as a delivery mechanism, providing the ability to deliver the functional gene to cells. The cells can then use the information to build the functional protein that the body needs, potentially reducing or eliminating the cause of the disease. Currently, gene therapy for the treatment of hemophilia A is available only as part of a clinical trial.  The AAV approach to gene therapy has been advanced at the University College London (UCL) in the treatment of Hemophilia B. At UCL, this technology has shown evidence to be both safe and effective, correcting bleeding for greater than four years in a continuing clinical trial.  

Live Webcast on Monday, Jan. 9 at 8:30 am PT, or 11:30 am ET

For full article, please click here.