Personalized medicine is a term we’ve heard for years. The ability to tailor a patient’s treatment type and dosage to obtain the best response is a holy grail for cancer researchers and clinicians. To this end, new technologies are in development which enable what is called “liquid biopsy” – a simple blood draw used to perform cancer diagnostics based on circulating biomarkers in the bloodstream, such as circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and exosomes. These new techniques and the associated players and market are at the core of Yole Développement’s analysis in its recent report, Liquid Biopsy: From Isolation to Downstream Applications 2018.
Yole’s analysts recently had the opportunity to interview Elodie Sollier, Chief Scientific Officer and Co-Founder, and Steve Crouse, Chief Commercial Officer, from Vortex Biosciences, one of this field’s key players. The company has developed an innovative technology based on microfluidics for isolating CTCs. Vortex launched its first product a few months ago and agreed to share with Yole’s analysts its vision of the liquid biopsy market. The following is a summary of their discussion:
(Source: Liquid Biopsy: From Isolation to Downstream Applications 2018 – Yole Développement, June 2018)
Yole Développemet: At Yole, we are convinced that ctDNA (circulating tumor DNA) and CTCs are complementary tools, and that both have advantages and drawbacks depending on what you’re looking for. However, over the past few years it seems ctDNA technologies have taken off much faster than CTC technologies. In your opinion, why is there more hype around ctDNA than CTCs? As a CTC player, how do you change people’s minds?
Vortex Biosciences: Vortex Biosciences was founded with the mission to revolutionize cancer diagnosis, monitoring, and treatment by replacing tissue biopsies with simple blood tests. The idea for the company started with an observation by Dr. Claire Hur at the UCLA Di Carlo Lab: that at higher flow rates, vortices formed in wider areas of a microfluidic channel, and that cells were trapped in these vortices . At the time, all of the circulating tumor cell (CTC) isolation technologies were complicated, did not release the cells for analysis, and relied on antibodies directed against EpCam, a marker for epithelial cells. Vortex Biosciences’ co-founders, Prof. Dino Di Carlo and Dr. Elodie Sollier, believed a better approach was needed to automate the isolation and collection of CTCs without molecular bias, and to release the cells to allow for phenotypic and molecular characterization.
We saw this “vortex technology” as a path to creating our new system. The company was founded in 2012 with funding from NetScientific PLC. Early work was focused on technology development, with the parameters of our proprietary chip being optimized . In 2014, NetScientific increased its funding to support development of our VTX-1 product. In late 2017 we commercialized the VTX-1 Liquid Biopsy System and are now selling this system in the US for research use applications . We have sales of the system and cartridges, along with installations, at many major cancer centers. Our business is now focused on moving CTCs into the clinical market and realizing the great clinical potential CTCs offer.
YD: What are circulating tumor cells (CTCs), and how can counting and retrieving these help patients?
VB: Cancer is the second-leading cause of death in the US, with 1,735,350 new cases expected in 2018 . Clinicians continue to rely on invasive tissue biopsies as a means to assess a patient’s disease and prescribe appropriate treatment regimens. Not only are tissue biopsies risky and expensive, they limit the understanding of a disease. Cancer is known to be heterogeneous, with multiple cell populations. Single-site tumor biopsies may not recapitulate intra-tumor heterogeneity, and may fail to reflect a patient’s genetic diversity. Furthermore, as a patient undergoes treatment, monitoring cancer status to allow for informed treatment adjustments is challenging, if not impossible .
Circulating tumor cells (CTCs) are cancer cells known to release into the bloodstream from both primary and metastatic tumors, spreading in the body to create metastasis. CTCs are considered the “seeds” of metastasis, which causes 90% of cancer deaths. CTCs are extremely rare events and surrounded by millions of blood cells, making their isolation challenging. However, collecting CTCs from a tube of blood provides a sample representative of all tumor cell populations, which can be easily collected frequently, providing real-time monitoring of tumor evolution, treatment effectiveness, and cancer metastatic risks [5-7].
(Courtesy of Vortex Biosciences)
The first test that utilized CTCs was approved by the FDA in 2004. The CellSearch system enumerated CTCs from a patient’s blood to predict the patient prognosis for colon, breast, and prostate cancer [8, 9]. More recently, new studies have been published to explore the clinical potential of CTCs beyond enumeration for prognostic value:
· Early Cancer Diagnosis: It’s usually assumed that CTCs are too rare to aid in early cancer diagnosis. But over the past 2 – 3 years, several publications have contradicted this assumption and suggested that CTC detection can be a powerful tool for early diagnosis. In 2014, Hofman’s lab at the University of Nice demonstrated that CTCs were identified 1 to 4 years prior to diagnosis by CT scan in at-risk non-small lung cancer (NSCLC) patients . Early in 2018, Dr. Tsai of the Linkou Chang Gung Hospital in Taiwan presented evidence that CTCs could be used as a more sensitive, specific biomarker than the current standard of care, which entails using stool samples for colorectal cancer diagnosis .
· Therapeutic Selection: Recent publications demonstrate that CTCs can play an important role in therapy selection, which is critical to ensure targeted, personalized care . A good example is lung cancer, where a biopsy is not possible in ~30% of cases. Standard assays to determine the best treatment path for NSCLC patients target a variety of biomarkers, such as EGFR mutations by qPCR, ALK, or ROS1 rearrangements by FISH, or PD-L1 protein measurements for immunotherapy selection [12-16]. Androgen receptor variant 7 (AR-V7) in prostate cancer is another important example for resistance detection to anti-androgen therapy [17, 18]. Many of these markers have now been confirmed to be present and relevant on CTCs, offering a new paradigm for this analysis.
· Cancer Monitoring during Treatment: Once a test is established for use with CTCs, it opens up the possibility of monitoring a patient’s disease throughout the course of treatment. Assays that could previously only be used at the time of diagnosis can now be applied at different times during the course of the disease and the patient’s treatment, informing how best to approach ongoing patient management [17-19]. This presents an amazing opportunity to create a truly personalized approach to each patient’s care.
· Early Detection of Cancer Recurrence: Detecting recurrence as early as possible also offers tremendous value. CTC enumeration has proven very valuable both in identifying a prognostic risk of recurrence and in early detection of cancer recurrence . For example, Dr. Sparano from the Albert Einstein College of Medicine demonstrated that the detection of CTCs 4 – 7 years after breast cancer remission enabled the identification of patients with a 22-fold higher risk of recurrence . In another study, Dr. Chinniah from the University of Pennsylvania showed that recurrence could be detected with CTCs in non-small lung cancer patients six months prior to a CT scan .
There are tremendous opportunities for CTCs to provide significant benefit to cancer patients and transform our current standard of care.
YD: Vortex’s technology is integrated onto a microfluidic chip. What is the science behind this, how does it work, and what are the advantages over existing technologies?
VB: Several technologies exist for isolating CTCs , but there is still an unmet need for label-free capture of intact CTCs in a simple, fully-automated manner, with the cells being released and preserved in suspension for various downstream assays.
The Vortex technology exploits inertial microfluidics and uses laminar microscale vortices to isolate and concentrate CTCs, which are usually large cells, from smaller blood cells. Here, CTC capture is based on cell size, cell shape, and deformability, and is agnostic of tumor biomarkers. The Vortex plastic chip consists of 16 parallel channels and nine serial reservoirs in each channel . At high flow rates, laminar microscale vortices develop in the rectangular reservoirs and trap larger cancer cells, while smaller blood cells pass through . The user interface is extremely simple. The one-time use Vortex Cartridge, containing the chip, the collection container, and the blood collection tube, is inserted into the VTX-1 Liquid Biopsy System. The blood is automatically transferred to the dilution tube for dilution with PBS buffer and injected through the microfluidic chip for CTC capture, while the flow-through is collected in the recycling tube .
VTX-1 Liquid Biopsy System (Courtesy of Vortex Biosciences)
After processing the entire volume of blood and executing a wash step to remove contaminating blood cells, the flow rate is lowered and the vortices dissipate to release the captured cells off-chip into their collection container. Depending on the operation mode selected by the user, the blood is transferred from the recycling tube and re-injected through the chip for a second cycle. The workflow is fully-automated, enabling CTC enrichment directly from a blood tube to the collection off-chip, in various containers of the user’s choice for different downstream assays . The Vortex chip is characterized and validated for CTC isolation from blood samples of metastatic cancer patients with breast, colon, lung, and prostate cancer. Numerous workflows are optimized for various CTC research applications, such as immunofluorescence staining and CTC enumeration, cytopathology and cytogenetics, Sanger sequencing, next-generation sequencing, and even Western-blotting on single cells [23-27].
Vortex technology was successfully applied for the CTC isolation from blood samples of patients with metastatic breast (N=22), lung (N=15), prostate (N=20) and colon (N=41) cancer. Each dot represents the CTC number per 7.5mL of blood from one patient blood draw.
(Courtesy of Vortex Biosciences)
The Vortex technology is ideal for isolating cancer cells from blood. It collects these larger cancer cells based on their size and deformability, but without filters that can get clogged or detain cells. This enables good CTC recovery, with very low white blood-cell (WBC) contamination, resulting in accurate, sensitive characterization of the CTCs. Cells are gently handled and remain viable such that the largest amount of information can be obtained. The process is simple, leading to a high level of reproducibility, and perhaps most importantly makes sample collection accessible to clinical labs. The isolation is also robust and label-free, requiring no antibodies, chemistry, or difficult-to-scale processes. Finally, the trapped cells can be easily released into different containers, giving a high level of flexibility to the user for the downstream characterization of the CTCs, either for research or clinical use. Ultimately, we believe all of these key product features will help clinicians and cancer patients at different stages of care to improve their outcome.
YD: In 2004, the CellSearch system was the first to gain FDA approval for CTC enrichment and enumeration. Almost fifteen years later, it is still the only one, though new technologies seem to be more performant. How do you explain this?
VB: CellSearch was way ahead of its time. When CTCs were first discovered, the belief was that CTCs could be biomarkers in and of themselves. In particular, early studies showed CTCs were indicative of a poor cancer prognosis. CellSearch focused on developing a system and a test that specifically addressed how best to provide a prognosis for a patient based on their CTC count. While this test worked well, it didn’t inform clinicians’ treatment decisions and thus fell out of favor. Today, the NPT codes are inactive and the test is rarely used in clinics.
There are a few reasons we believe this initial test did not have clinical success. First, the test did not characterize the cancer biology that is readily available in the CTC and necessary for making clinical decisions. Second, CTC recovery relied on EpCAM proteins expressed on the CTCs’ surface . The expression of and binding of these proteins by the CellSearch system was variable, resulting in low numbers of CTCs captured and leading to a false perception in the market that CTCs may not be useful for clinical applications. This perception still exists today, despite numerous studies that have demonstrated clinical utility for isolating and characterizing CTCs .
In the last 10 years, a number of new technologies have entered the market to isolate CTCs. Many of them have been demonstrated to be better at isolating CTCs than the CellSearch system. None of them, however, were developed with a clinical product in mind. The issues with these systems range from complicated workflows to isolating CTCs with molecular bias, to CTCs being stuck on the isolation cartridge, to cells not being viable. The ideal system simply has not been developed to help address the clinical opportunity that CTCs offer. We believe the VTX-1 is finally the right product to help realize that full clinical potential. It is automated, simple to use, captures CTCs with high purity and high recovery without molecular bias, releases CTCs after isolation for characterization, and keeps the CTC intact and viable.
Finding the right level of funding to support clinical trials and reach the clinical market continues to be Vortex’s biggest challenge, but I am confident we’ll work that out and in the very near future have clinical assays utilizing CTCs to help patients.
YD: When do you think we will see another system approved for clinical use? How does Vortex work towards validation of its system and assays?
VB: The CellSearch system was approved for prognostic use. This provided a simple approach towards the clinical trial, resulting in approval. However, prognosis is not valuable for determining therapeutic decisions. Clinicians didn’t change their treatment decisions based on the results; thus the technology lost favor. We believe that simply achieving FDA approval for a system is insufficient if we want CTCs to meaningfully change the standard of care. We must demonstrate integrated workflows that provide clear diagnosis in a way that can influence how a patient is cared for. Therefore, clinical trials must be designed to achieve this. The challenge is, these types of clinical trials are expensive and time-consuming. The good news is, a couple of companies offer laboratory developed tests (LDTs) today through their labs. For example, Biocept offers mutation profiles like EGFR on both CTCs and ctDNA , as well as CTC enumeration assays. Genomic Health and Epic Sciences recently announced they will be selling a test for AR-V7 protein detection in prostate cancer, which will have Medicare coverage starting in July 2018 . The Epic Sciences and Biocept technologies are further from FDA approval only because their instrument is not ready for placement in a clinical lab. However, we see CTCs beginning to be part of the clinical standard of care today.
We believe the VTX-1 is ready to be in a clinical lab and we are working with diagnostic partners to move CTC isolation and associated assays towards FDA approval. However, we don’t believe the approval lies with the CTC instrument, but rather with integrated assays that provide clinical answers. In the end, the CTC isolation system is really the enabling technology that provides a sample with amazing access to cancer biology. It is what you do with this access that will lead to the right answers, and consequently real value for patients. We currently have programs on EGFR and PDL-1 in NSCLC and AR-V7 mRNA detection in prostate cancer among others, where we are performing clinical studies to inform an eventual clinical trial [31, 32].