Gilead Sciences (GILD) reported final results from its phase 1 study using its CAR-T cell therapy KTE-X19 to treat patients with relapsed/refractory acute lymphoblastic leukemia (ALL). This was early clinical data that was presented at the American Society for Clinical Oncology (ASCO) 2019 meeting. The goal of the treatment is to provide a more safe and effective way of treating this relapsed/refractory cancer patient population.
Preliminary Data Shows KTE-X19 To Be Effective
The results that were presented came from a phase 1 trial known as the ZUMA-3 study which recruited patients with relapsed/refractory acute lymphoblastic leukemia. ALL is a blood cancer that affects the bone marrow and white blood cells. This study was done as a single-arm study, which means there was no placebo involved. However, KTE-X19 did achieve some impressive results for this hard to treat population. I state hard to treat patient population because these were ALL patients that were relapsed/refractory after two or more prior lines of treatment. Patients were given one of the three doses in question:
- 2 x 10 6 cells/kg
- 1 x 10 6 cells/kg
- 0.5 x 10 6 cells/kg
Despite these patients failing on two prior therapies, there were some impressive response rates observed in this phase 1 study. Of the 41 patients who received one of the above doses for KTE-X19, 68% achieved a complete response (CR) or complete response with incomplete hematologic recovery (CRI). Then, 100% of these patients that responded had undetectable minimal residual disease (MRD). I must emphasize this point about MRD. That's because MRD that is found during or after treatment is a big cause of a cancer relapse. The fact that no MRD was detected means the treatment worked very well for these specific group of patients that responded. This study was important in determining if KTE-X19 could achieve a strong response rate in this relapsed/refractory ALL population. That's important, but the basis of this study was to look at what dose would be appropriate for a phase 2 study. The current phase 2 study is using the 1 X 10 6 cells/kg dose of KTE-X19. There were 23 patients total that had received this dose. About 19 were evaluable for efficacy of this specific dose group. It was noted that 84% (16 patients) achieve a CR or CRi. Then about 75% (12 patients) had an ongoing response.
Safety Is Key For Success of KTE-X19
The efficacy of this phase 1 ZUMA-3 study was established using KTE-X19 to treat patients with relapsed/refractory KTE-X19. The problem is that the use of cell therapy can involve some safety concerns. That's exactly what happened in the study. Nothing that couldn't be solved, but Gilead had to implement a revised adverse event management protocol. That's because there were about 29% of Grade ≥3 cytokine release syndrome (CRS) events. On top of that, there were 38% of neurologic events that had occurred. That's not good for these patients, but then, there were 2 patients that had experienced Grade 5 adverse events. One patient had a stroke because of CRS and neurologic event. The second patient had gone through multiorgan failure secondary to CRS. Cytokine release syndrome occurs when immune cells release a large amount of cytokines in a rapid fashion. These cytokines are released into the bloodstream causing a host of problems for the patient. Immunotherapies are the culprit for CRS. While efficacy was strong, which I have noted above, there was a minor bump in terms of safety. However, the company immediately implemented an adverse event management protocol and the issue was quickly resolved. After the implementation of the protocol in about 9 patients that took the 1 x 10 6 cells/kg dose of KTE-X19, there were no Grade 4/5 events.
Cell Therapy Market Expansion
Gilead still has a long way to go with its Yescarta treatment, which was approved in the United States back in October of 2017 and then in Europe in August of 2018. Since then, sales have been kind of slow. The good news is that sales are starting to grow year over year. For instance, in Q1 of 2018, Yescarta sales were $40 million. In Q1 of 2019, sales of Yescarta came in at $96 million. That's a 140% year over year increase in sales. The large uptake during that time was driven by the notion of adding a lot more patients to Yescarta treatment. The best part of all is that Gilead expects its yearly revenue for Yescarta to double in 2019. This should be possible as the company has 75 authorized Yescarta centers in the United States and then about 25 in Europe.
Gilead obtaining positive results from its phase 1 study using KTE-X19 to treat patients with ALL is good news as it looks to expand its cell therapy platform. With the ability for annual revenue for Yescarta to double that will indicate that the company is starting to grow this part of its business. The risk is that it still won't be easy to get payers on board to cover the costs of treatment. Especially, since it costs about $375,000 per treatment. Still, Gilead is trying to expand its therapy to additional centers and Yescarta is at least growing sales by 140% year over year. Whether or not this growth is sustainable remains to be seen, but things are looking pretty good for now. The other risk is the early stage KTE-X19 program itself. That's because the reported results were only a phase 1 study. There is still a long way to go to get this cell therapy through other large studies. Especially, since the phase 2 is ongoing for the time being. In addition, the treatment still has to be approved by the FDA. There is no guarantee that the FDA or any other regulatory agency will ultimately approve it.
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