Antigen-specific technology: Building the Tr1 pipeline
The immune system needs to protect against pathogenic bacteria and viruses in the intestine but also needs to tolerate the many benign bacteria and food components as a reaction to these stimuli can cause intestinal damage. In 1997, Groux et al published a paper in Nature on a new type of regulatory T-cell. Asseman 1998 provides a good commentary. The area has been recently reviewed by Zeng (2015).
Groux showed that naïve CD4+ T-cells exposed to a specific food antigen produced a subset of T-cells, which he named T regulatory cells type 1 (Tr1). These prevented effector T-cells from responding to specific foreign food antigens so causing a pathological response to the intestine. Tr1 cells therefore have a crucial antigen-specific protective effect Tr1 cells are characterised by production of very high levels of IL-10. The high IL-10 levels stopped other T-cell cell types (Th1, Th2) from developing. Groux et al used ovalbumin as the antigen. Antigen presenting cells (APCs) ‘present’ specific antigens to naïve CD4+ T-cells so they become Tr1. Tr1 can also protect against autoimmune diseases for example Pot 2011.
As a natural cell, Tr1 cannot be patented but the process of generating Tr1 cells against a specific antigen can be protected. TxCell holds a granted process patent, EP1739166B1 (expiry 1 July 2025), and has filed a patent application, WO 2009068575 A1 (expiry 28 November 2028). The patent claims “at least one human Tr1 cell population directed against a food antigen from common human diet”. The ASTrIA method involves harvesting leukocytes from human blood and stimulating them with antigen. For Ovasave the antigen is ovalbumin. The resulting ovalbumin-specific Tr1 cells are then cultured, harvested, purified and frozen in single dose aliquots. A blood sample of 150ml is stated to produce between 30 and 50 doses: about a three-year supply. The cells are autologous, that is they are injected back into the donor, who is also the patient.
The method described in these two core patents can be applied to a variety of antigens. The pipeline is summarised in Exhibit 2. The immediate focus is Ovasave in inflammatory bowel disease (Foussat 2003) specifically Crohn’s. There is also published preclinical work using the ovalbumin model on central nervous system inflammation (Barrat 2002).
Exhibit 2: TxCell pipeline
Product |
Indication |
Stage |
Timelines |
Comments |
Ovasave |
Refractory Crohn’s |
Phase IIb |
Autologous Tr1 cells, in a 56-patient randomised, two-arm placebo-controlled European study. Restart by mid-2016, data Q118. |
Regulatory approval received for the amended study protocol with MaSTherCell as the manufacturer. The open IND in the US could allow a US centre to participate. The trial is over 32 weeks per patient; the first six weeks are double blind. |
Col-Treg |
Uveitis |
Preclinical |
Start 2016-2017 |
Tr1 cells against Type II human collagen. |
CAR Teg |
Lupus nephritis |
Research |
Clinical trials possible from 2018-19, multiple possible products inc multiple sclerosis |
CAR Treg platform being developed. Lupus nephritis, a severe complication of lupus, is the designated lead indication. |
Source: Edison Investment Research based on TxCell corporate presentation January 2016
Mechanism of action of antigen specific Tr1
Exhibit 3 shows possible localised mechanisms of action (MoA) suggested by TxCell. As with most cell therapies, the cells probably exert an effect through multiple routes.
Exhibit 3: Potential mechanism of action
Mechanism |
Notes |
IL-10 secretion |
The Tr1 cell type naturally expresses a high level of Interleukin -10 (IL-10). IL-10 is a potent anti-inflammatory cytokine that generally reduces immune activity. IL-10 was being developed by Schering-Plough as Tenovil (Ilodecakin) but was discontinued as trials showed that systemic IL-10 had no efficacy in Crohn’s disease, although it did help to prevent the disease re-occurring once it was controlled; Marlow 2013 has reviewed the area. Most Crohn’s patients have normal to high IL-10 levels. Scientific work has focussed on localised IL-10 as the key immune suppressing agent, for example Pot 2011. |
IL-13 secretion |
Tr1 cells express high levels of this cytokine. It is closely related to IL-4 so might stimulate Tr1 growth. There is no known association between IL-13 and Crohn’s disease (Biancheri 2014). IL-13 appears to have some anti-inflammatory proprieties, similar to IL-4, but this role is not well defined. IL-13 is known to be associated with allergic lung disorders, asthma and resistance to parasitic disease. Watson (1999) observed anti-inflammatory activity with suppression of eosinophil recruitment in an antigen-challenge Guinea Pig lung model. |
CD39 |
CD39 is a membrane bound enzyme found on various cells including Tregs. It catalyses the conversion of extracellular ATP to AMP. An associated enzyme, CD73, then converts AMP to adenosine, which is anti-inflammatory. ATP is released in inflamed locations either directly by cells or as a result of cell lysis and promotes the inflammatory response. There is some literature on the role of CD39 in inflammatory bowel disease, for example Antonioli 2014. Friedman 2009 found that lack of CD39 increased susceptibility to inflammatory bowel disease. Gibson 2015 in a small clinical study (of whom 25 were Crohn’s patients) noted an inverse association between CD39 levels and disease severity with 8% showing CD39 at peak disease vs 22.5% in remission; this was statistically significant. |
Source: Edison Investment Research, TxCell reports
The concept behind the use of ovalbumin is that, as a common food antigen, it will be frequently present in the intestine and some will be absorbed by special immune areas in the intestine wall called Peyer’s patches.These are specialised structures in the intestine wall that take in antigens to induce tolerance (food) or activate an immune response (pathogens). Antigens are passed to the mesenteric lymph nodes that protect the body from infection originating in the intestine.
For efficacy, ovalbumin has to pass through the intestine lining, be taken up and processed by APCs and then displayed as fragments in MHCII to stimulate the Ova-Treg cells to exert some form of localised immune regulation. The Ova-Treg cells need to migrate from the administration site to the intestine lining and the intestinal mesenteric lymph nodes. Ovalbumin does not affect the migration but T cells migrate to areas of inflammation due to other cytokine signals.
To get regular ovalbumin in the diet, the Phase I/IIa patients “ingested an ova-enriched diet in the form of a daily meringue cake”. Note that there is no clinical meringue dose response curve but that animal studies indicate that only a trace amount is required. A normal diet may be adequate.
It would seem likely that patients have frequently been exposed to ovalbumin and may already have endogenous Ova-Tregs. Native ovalbumin is resistant to proteolytic cleavage in the stomach (Walker 1978) and in mouse models, high levels of radiolabelled ovalbumin pass along the small and large intestines (Oliveira 2007). Oliveira et al also showed that ovalbumin locates to Peyer’s patches and moves to mesenteric lymph nodes. This is important for a systemic effect since Crohn’s disease commonly occurs in the lower small intestine and large bowel and rectum whilst most intact ovalbumin in the intestine will be in the upper bowel. Cooking of ovalbumin, as in meringue, exposes new proteolytic sites in the protein to enzyme action (Nyemb 2014) and bile salts and lipids in the duodenum (upper small bowl) increase digestion (Martos 2010). Golias et al (2012) found that cooking altered ovalbumin digestion and allergic response.
The Ovasave Phase I ran between 2008 and 2010 and was published in 2012 (Desreumaux 2012). Details and comments on the study are in Exhibit 4.
Exhibit 4: Phase I design and outcomes
Aspect |
|
Notes |
Doses tested |
. |
The trial tested four single dose levels of autologous ova-Treg cells: 106, 107, 108 and 109. |
Preclinical dose data |
|
Groux 1997 noted in a mouse model that 2x105 cells prevented inflammatory bowel disease. A lab mouse is about 20 grams in weight: 3,500-fold difference to a 70kg human. Hence, one would expect a human dose of about 108-109 cells. We note that mice are very different to humans. For a rough dose comparison, in the TiGenix Phase III in fistulating perianal Crohn’s disease, the effective therapeutic dose was 1.2x108 cells injected into a highly concentrated zone, although this used different cells with a different indication and use. |
Cohort sizes |
Planned |
The initial cohort had six patients with planned three per cohort then an extra six at the highest dose. The study was open label. That is normal for an early stage dose and safety study especially for cell therapies. |
|
Actual |
As the best dose seemed to be 106, this cohort was increased from six to eight. The 107 and 108 groups had three patients, with six in the 109 group. |
Patient response to biological agents |
Most (19/20) patients had failed on at least one anti-TNF therapy; in the eight patient 106 dose group, five (62.5%) had failed on three and the other three had failed on one. |
Efficacy assessment |
|
Patients were assessed using the Crohn’s Disease Activity Index (CDAI, see below) at weeks one, two, three, five, eight and 12. Response was a decrease in CDAI of greater than 100 points with remission defined as a score of 150 or less. |
Biomarkers used (see Chang 2015) |
C reactive protein (CRP) |
CRP is a marker of general inflammation. CRP is produced by the liver in response to inflammation and detected by a cheap blood test. |
Calprotectin |
Calprotectin is a protein released by activated neutrophils at an inflamed site. In inflammatory bowel disease it can be conveniently detected in faecal samples. Faecal calprotectin is specific to inflammatory bowel disease although levels do not necessarily correlate with clinical disease scores. |
106 dose outcome |
|
The data showed that 75% (6/8) of the 106 dose group showed a response, with three entering remission by week 5 and two remaining in remission at week 8. One patient, with a CDAI score of over 500, did not show any response at all (and did not provide Week 8 data). Note Crohn’s is a variable disease. At five weeks (not prespecified), helped by an erratic-looking one-off score of 50, the average decrease was 143 points with a standard deviation of ±105 (the 95% confidence interval was between +63 and -349). This was statistically different to the baseline score, p= 0.039 using the Wilcoxon signed rank test. CRP levels showed high variability over the 12-week trial and there was no effect on calprotectin levels. |
Higher dose outcomes |
|
One patient in each of the 107 and 109 dose groups responded. No patient responded at 108. Immune products often have a low dose maximum as any strong immune responses are damped down by regulatory mechanisms. |
The Phase I and II studies use the CDAI score as an endpoint (Exhibit 5). This was devised in 1977 (Best 1976) and has been widely used since. The system has no specific upper limit, but a score under 150 points is deemed remission, and over 450 points is severe disease. Crohn’s is a condition subject to sudden flares then remission, so variability is expected. Note that the data is not controlled and could be subject to small number effects (in a small group, one or two outliers make a big difference to the average; in a large group, such outliers are averaged out and we see reversion to the mean).
Exhibit 5: Crohn’s Disease Activity Index (CDAI)
Criteria |
Subgroup criteria |
Multiplier |
Number of liquid or soft stools each day for seven days |
x 2 |
Abdominal pain (graded from 0-3 on severity) each day for seven days |
x 5 |
General wellbeing, subjectively assessed from 0 (well) to 4 (terrible) each day for seven days |
x 7 |
Presence of complications, Score one for each of: |
x 20 |
|
the presence of joint pains (arthralgia) or frank arthritis |
|
inflammation of the iris or uveitis |
|
presence of erythema nodosum ((inflation of the fat deposits underlying the skin), pyoderma gangrenosum (ulcerating autoimmune skin disease) or aphthous ulcers (mouth ulcers / cankers) |
|
anal fissures, fistulae or abscesses |
|
other fistulae |
|
fever during the previous week |
Taking Lomotil or opiates for diarrhoea |
x 30 |
Presence of an abdominal mass (0 as none, 2 as questionable, 5 as definite) |
x 10 |
Haematocrit of <0.47 in men and <0.42 in women (haematocrit is the proportion of red cells in blood) |
x 6 |
Percentage deviation from standard weight |
x 1 |
Exhibit 6 shows the average scores for the 106 group – the optimal identified dose, but this conceals some very erratic scores. A simplified per patient data plot is in Exhibit 6. The data in Exhibit 5 was used to set the Phase IIb endpoint at Week 6, with the assumption that efficacy declines thereafter as the ova-Treg cells die.
An issue with the CDAI is that it does not provide a measure of inflammation such as CRP. CDAI has been critiqued as a marker for testing biological therapies, for example Binion 2010.
Exhibit 6: Average response 106 dose
|
Exhibit 7: Individual patient responses, 106 dose group
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|
|
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Exhibit 6: Average response 106 dose
|
|
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Exhibit 7: Individual patient responses, 106 dose group
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Ovasave Phase IIb: CATS29
The CATS29 study is a randomised, double-blind, placebo-controlled study to evaluate the performance of a single 106 cell dose of Ovasave in refractory Crohn’s disease patients over six weeks, Exhibit 8. It is designated Phase IIb by TxCell. A second, open-label phase of the trial is then planned to provide additional safety data and possibly some uncontrolled data on efficacy and responses. Adding this open-label study where all are treated is designed to aid recruitment. The redesigned study protocol has regulatory approval and will restart soon with data in Q118.
The role of the CATS29 Phase II is to get enough clinical evidence to gain a strong partnering deal. The weakness of CATS29 is that it only tests a single dose and at only one dose level. Patients are not supposed to take other therapies but this might be hard to control and will result in them being counted as therapy failures if detected.
MaSTherCell, a contract manufacturing organisation (CMO) based in Belgium, was contracted to supply Ovasave during 2015 and technology transfer is underway. Regulatory approval of this move, expected by mid-2016, is needed before CATS29 can restart. A five-year strategic agreement was signed in December 2015 so that MaSTherCell will supply all TxCell cell products.
In July 2015, TxCell gained an FDA fast track and open IND for Ovasave, so it could add a US centre into the CATS29 study. PCT, a Caladrius subsidiary, was appointed in March 2016 as TxCell’s contract manufacturing partner in the US. It is likely that some US patients in one or two centres will be enrolled in CATS29 when it restarts.
Exhibit 8: Design of CATS29 Phase IIb study
Aspect |
Comments |
Initial design |
The initial design tested three dose groups plus placebo and required 160 patients. The clinicaltrials.gov entry, NCT02327221, will be updated once the new design is approved. TxCell dosed fewer than 10 patients up to June 2015. |
Patient selection |
CATS29 patients have to score ≥250 points on CDAI to enter the study. These patients must have failed on at least one biological therapy and would be unresponsive to standard immune suppressing therapies. |
Current design |
In the new design, 72 eligible patients give 150ml of blood. This is processed into Tr1 ovalbumin specific antigen cells (Ova-Treg) in a process that currently taskes12 weeks. TxCell has to over recruit as patients need to meet the criteria of CDAI ≥ 250 (see below) with positive CRP and calprotectin markers both on enrolment and about three months later on dosing. Inevitably, some patients will fall below the 250 CDAI level, since Crohn’s is an episodic disorder, while their cells are being prepared so will not be dosed. In addition, not all patient blood samples will produce Ova-Treg cells in sufficient quantity or quality. TxCell requires 56 assessable patients for the endpoint. |
Stage one |
The initial six-week phase is a double-blind, placebo-controlled evaluation of a single 106 cell infused dose vs placebo The endpoint is a response based on the CDAI score assessed at week 6. |
Primary endpoint |
A response is defined as a reduction of ≥100 points in the Crohn’s Disease Activity Index (CDAI, Exhibit 5). TxCell expects a response difference of 70% treated vs 30% placebo. |
Power |
If all 28 patients per arm complete the study, the power is expected to be 80%. Statistical power is the probability that the clinical trial will have a significant (positive) result of p≤0.05 assuming that the real difference between treated and placebo is as anticipated. In other words, if Ovasave works, there is an 80% chance that this trial will be positive. |
Stage two |
This is an open-label phase in which all patients receive 106 cells at weeks 8, 16 and 24 with final assessment at week 32. There is a three-year safety follow up as this is a cell therapy product. This stage is designed to be attractive to patients and to aid recruitment since all will receive the stem cells. |
Aspect |
Initial design |
Patient selection |
Current design |
Stage one |
Primary endpoint |
Power |
Stage two |
Comments |
The initial design tested three dose groups plus placebo and required 160 patients. The clinicaltrials.gov entry, NCT02327221, will be updated once the new design is approved. TxCell dosed fewer than 10 patients up to June 2015. |
CATS29 patients have to score ≥250 points on CDAI to enter the study. These patients must have failed on at least one biological therapy and would be unresponsive to standard immune suppressing therapies. |
In the new design, 72 eligible patients give 150ml of blood. This is processed into Tr1 ovalbumin specific antigen cells (Ova-Treg) in a process that currently taskes12 weeks. TxCell has to over recruit as patients need to meet the criteria of CDAI ≥ 250 (see below) with positive CRP and calprotectin markers both on enrolment and about three months later on dosing. Inevitably, some patients will fall below the 250 CDAI level, since Crohn’s is an episodic disorder, while their cells are being prepared so will not be dosed. In addition, not all patient blood samples will produce Ova-Treg cells in sufficient quantity or quality. TxCell requires 56 assessable patients for the endpoint. |
The initial six-week phase is a double-blind, placebo-controlled evaluation of a single 106 cell infused dose vs placebo The endpoint is a response based on the CDAI score assessed at week 6. |
A response is defined as a reduction of ≥100 points in the Crohn’s Disease Activity Index (CDAI, Exhibit 5). TxCell expects a response difference of 70% treated vs 30% placebo. |
If all 28 patients per arm complete the study, the power is expected to be 80%. Statistical power is the probability that the clinical trial will have a significant (positive) result of p≤0.05 assuming that the real difference between treated and placebo is as anticipated. In other words, if Ovasave works, there is an 80% chance that this trial will be positive. |
This is an open-label phase in which all patients receive 106 cells at weeks 8, 16 and 24 with final assessment at week 32. There is a three-year safety follow up as this is a cell therapy product. This stage is designed to be attractive to patients and to aid recruitment since all will receive the stem cells. |
Source: Edison Investment Research based on TxCell statements and presentations
Phase III, partnering and probabilities
A positive primary endpoint by Q118 should enable a partnering deal, perhaps by late 2018. Timing of such deals is hard to forecast. Assuming this timeline is met, the trial protocol and manufacturing system needs to be in place before any Phase III can start. However, it is probable that a small multi-dose Phase IIb will be required before a multi-dose Phase III. Note that a few patients have already received multiple Ovasave doses, two for up to a year. Management expect the Phase III to be funded by a global partner that will also manufacture.
Manufacturing of Tr1 autologous cells is a multistep process. TxCell is working hard to reduce the number of stages, optimise the yield of each stage and reduce manual interventions required. It is working with the UK Cell Catapult, a government-backed centre of expertise, and various equipment manufacturers. As a final concept, a fully automated system is desirable with Tr1 cell culture in sealed units. This should provide optimum yields, an ability to scale up throughput (each patient is one batch so the process is replicated), and get a low cost of goods, perhaps about 10% of the average revenue. However, it is not certain how automated the final system will be. The partner will need to transfer this optimised process to its own facility or designated CMO and gain regulatory approval, although they could use TxCell’s current contractors for the trials. A US product requires a US cell manufacturing site; this can take at least nine months to establish and validate. A deal in Q418 therefore implies a trial start in H219 or later.
A multi-dose Phase III with 12-month dosing could take three years, so if started in H219, data might be reported in late H222. We forecast sales from late 2023, but 2024 is realistic.
The success probability of Ovasave is hard to assess. Classical Phase IIb projects have a 20-40% probability. Although TxCell views the probability of success as being very high, the limited Phase I data (three clinical remission cases out of eight by week five) suggests a clinical 33% probability in line with our general caution about cell therapy. We have applied a further 85% probability of developing an automated manufacturing system on time and to acceptable regulatory and commercial standards. This gives a combined 28% probability.
Potential market for Ovasave in Crohn’s disease
The current definable market for Ovasave is in Crohn’s disease where patients have received biological therapy but have proved either refractory or relapsed or have experienced severe side effects. Exhibit 9 gives the Edison summary market assessment. Exhibit 10 shows the assumptions and sources used. Although Europe should have a similar or greater number of cases, lower diagnosis and biological therapy use rates compared to the US lower the market potential.
Exhibit 9: Edison market assumptions on Ovasave
Market segment |
Sub segment |
% of NA market |
North America |
% of Eur Market |
Europe |
% of JP market |
Japan |
Total |
Total population |
|
|
656,750 |
|
762,200 |
|
26,924 |
1,445,874 |
Adult cases |
|
93% |
610,778 |
95% |
724,090 |
93% |
25,578 |
1,360,446 |
Biological |
|
16.7% |
102,000 |
10.0% |
72,409 |
20.0% |
5,116 |
179,525 |
Share of biological treated cases accessible to Ovasave |
Initial non-response |
35% |
35,700 |
35% |
25,343 |
35% |
1,790 |
62,833 |
Severe side effects |
10% |
6,630 |
10% |
4,707 |
10% |
333 |
11,670 |
Secondary non-response |
20% |
13,260 |
20% |
9,413 |
20% |
665 |
23,338 |
Potential Ovasave market |
|
55,590 |
|
39,463 |
|
2,788 |
97,841 |
Source: Edison Investment Research based on TxCell data and literatures sources as in Exhibit 10
At least 25% of the above patients might have perianal disease (de Zoeten 2013), of whom half have fistulas, channels between the intestine and skin or vagina. It is not certain how Ovasave therapy would relate to these complications. The assumption made is that perianal disease does not affect Ovasave use. Stem cells have already been shown to be useful in Crohn’s: the Phase III study of Cx601 from TiGenix has shown that it accelerates complex perianal fistula healing.
A commercial analogy to Ovasave might be Entyvio (vedolizumab, Takeda) approved for Crohn’s disease by the FDA and EMA when other treatments have failed. The UK NICE organisation issued guidance in August 2015 that Entyvio is useful, but only at a discounted price (undisclosed), for active Crohn’s disease if biological therapies have failed. Entyvio has a UK list price of £2,050 per 300mg dose, costing about €25,830 in year one, then about €18,450 for subsequent years if the disease remains active and Entyvio continued to be effective. In the US, prices are higher, with Entyvio costing $43,371 for the first year (€37,750) and $33,733 subsequently. Remicade before biosimilar erosion costs $31,856 in year one and $24,777 subsequently. TxCell notes that other current biological agents cost €22,000.
Our forecast assumes (see Exhibit 10) an EU list price for Ovasave of €30,000 based on a premium to the cost of the first year of Entyvio, The US price assumed is €45,000. The average biological price will fall in future as biosimilars enter the market, but the Ovasave market segments should not be affected by this and may expand if biological use becomes more affordable and widespread. This would create more refractory patients - but maybe these will be more price sensitive. Inflation of 2% is assumed from 2018.
TxCell assumes that 80% of patients will receive regular six-weekly doses of Ovasave in year one, dropping to 60% in year two and 30% in year three. These appear to be arbitrary assumptions, but seem reasonable and have been followed by Edison. The current production system produces in effect three years’ worth of therapy in one run. This makes the economics for TxCell’s partner front-loaded: the first dose has a very high cost of goods as custom made but subsequent doses just carry storage and logistics costs. We also assume that a core of 25% of patients stay on Ovasave therapy in year four, declining at 25% year-on-year. It is known that some patients remain on anti-TNF therapy for long periods. Longer-term use will require a further cell batch to be made.
Exhibit 10: Crohn’s disease market data and assumptions
Data |
Edison estimate |
% cases |
Sources and commentary |
Adult prevalence of Crohn’s disease |
1.44m |
100% |
One of the confounding factors in assessing prevalence is the difficulty of diagnosis as it can be difficult to separate ulcerative colitis from Crohn’s disease. The prevalence is high because the condition is long lasting, but the disease is episodic so not all patients need treatment all the time. Loftus 2002 found that “Most patients have a chronic intermittent disease course, while 13% have an unremitting disease course and 10% have a prolonged remission”. Incidence levels (new cases) are very low at about 10-12 per 100,000 per year, so about 5% of prevalence rates. This epidemiological data therefore needs to be treated with some caution. The Center for Disease Control estimates 201 per 100,000; Kappelman 2013 using insurance claims found 241/100,000. The US population is approaching 320 million, with Canada at 35 million, so this gives about 610,000 adult Crohn’s cases; adults are 93% of all cases. The current EU population (28 states) is 507 million, so about 940,000 cases are expected. However, this includes a number of states where higher priced therapy will be less available. Further, it excludes rich counties like Switzerland and Norway. Adjusting for these gives an accessible European population of about 412 mi, so 724,000 adult cases in theory. However, the rate of diagnosis varies across European countries; for example, in the UK Stone 2003 found 130 cases per 100,000 whereas Hein 2014 in Germany noted 322 per 100,000 using insurance data. Lucendo 2014 found 137/100,000 in Spain. Japan claims a very low rate of 21.3/100,000 (Asakura 2009), about 10% of the likely European and US rate. |
Proportion on biological therapy |
205,000 |
13-20% |
Use of biological agents is fairly stable and healthcare providers have often tried to optimise the dosing of such drugs due to their cost. Patients may cycle between agents, so there will be a degree of patient churn as patients drop out if in remission and new patients start. Edison uses a value of 15% on this, but there is no data to support this. The UK NICE recommends review after a year of therapy with the aim of discontinuing therapy if the patient is in remission. However, patients often wish to stay on therapy to avoid further attacks. The assumption is that only patients that have failed on at least one biological therapy will be eligible for Ovasave and these will tend to be moderate to severe disease categories. The estimate for patients on biological therapy in the US is derived from market research from TxCell. Edison estimates about 102,000 Crohn’s patients on anti-TNF therapy in the US and Canada. The evidence for other countries does not appear as robust: TxCell data indicates that about 13.5% of European CD patients are using biological agents. Edison estimates about 98,000 patients. Japan might add a further 5,000. Japan has a novel system for regulating cell therapies, enabling faster approval and reimbursement. This gives about 205,000 potential patients on biological therapy. This number will be subject to a natural level of churn as some patients gain prolonged remission and others start therapy. Lower biosimilar prices may also encourage biological use over the next decade. |
Unresponsive |
72,000 |
35% |
Biological agents generally claim a response rate of about 65% (see Panaccione 2010 for a review). Hence, 35% are eligible for Ovasave therapy – several biological agents may be tried first. Roda 2016 noted a high level of unresponsive or relapsed patients and attributes this to the antibody responses against the monoclonal antibodies used. Ovasave will avoid that issue. |
Side effect withdrawal |
13,000 |
10% |
The rate of withdrawal due to side effects of biological drugs in trials is about 10%, although it is not always clear why. In CLASSIC II (see below), the open-label withdrawal rate was 11.3%. |
Relapsed |
27,000 |
20% |
Of the 65% who respond initially to biological therapy, TxCell estimated in 2014 that 20% would relapse. The CLASSIC II trial (Sandborn 2007) with Adalimumab looked at patients who were either initially in remission or responsive but not in remission. Of those in remission, 79-83% remained in remission at 56 weeks after maintenance therapy. Edison estimates about 27,000 possible prevalence cases. |
Source: Edison Investment Research
Exhibit 11: Progression of Crohn’s disease and role of Ovasave
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Source: TxCell presentation
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Forecasting the Crohn’s disease market
The figures in Exhibit 9 are for prevalence. We assume that there is a turnover rate of 20% of biological patients per year; the incidence rate overall is about 5% of the prevalence rate. If the Ovasave market share is over 20%, the prevalence number reduces assuming patients try a course of Ovasave once only (note they receive multiple doses for up to three years from each custom manufactured batch). Turnover is due to the episodic nature of the disease and by the restraints imposed by healthcare providers to avoid substantial long-term costs with no clinical gain. Exhibit 11 shows the time course with patients often cycling between biological agents.
This might be offset commercially by longer periods of use. To model these potentially longer-term patients, we assume a fourth year of use by 20% of patients, with the number declining at 25% per year. All these are simplistic assumptions for the purposes of modelling.
The effects are shown in Exhibits 12 (EU) and Exhibit 13 (US) for the number of patients. Note that the x-axis shows years after launch, assumed to be 2023-4 for valuation, but uncertain.
Exhibit 12: European patient numbers
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Exhibit 13: North America patient numbers
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Source: Edison Investment Research. Note: Not probability adjusted.
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Source: Edison Investment Research. Note: Not probability adjusted.
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Exhibit 12: European patient numbers
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Source: Edison Investment Research. Note: Not probability adjusted.
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Exhibit 13: North America patient numbers
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Source: Edison Investment Research. Note: Not probability adjusted.
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At this stage in Ovasave’s development, it is not feasible to assess the competitive profile fully. The few possible alternatives are all yet to produce definitive data. In the cell area, Mesoblast has a Phase III study with Prochymal, due to report mid-2017, in resistant Crohn’s disease.
The main action in biosimilar development will not affect Ovasave and might expand the market. In the area of anti-TNF resistant Crohn’s disease, AbbVie has a major, 210-patient Phase II dose finding study running with a small molecule JAK inhibitor, ABT494 (NCT02365649). This reports in December 2017 and could reach the market before Ovasave, but the primary indication will be rheumatoid arthritis. It could be a powerful competitor if it works well, since as a small molecule it could be less expensive and easy to administer. Roche has a “dual-action anti-integrin” antibody, Etrolizumab, similar to Entyvio, which is targeting both anti-TNF naive and -refractory patients (NCT02394028). This trial reports in 2018 so could be marketed from 2020.