A Cancer Research UK First Time in Human Phase I Trial of IMA950 (Novel Multipeptide Therapeutic Vaccine) in Patients with Newly Diagnosed Glioblastoma

Abstract

Purpose:
To perform a two-cohort, phase 1 safety and immunogenicity study of IMA950 in addition to standard chemo-radiotherapy (CRT) and adjuvant temozolomide in patients with newly diagnosed glioblastoma (GBM). IMA950 is a novel GBM specific therapeutic vaccine containing 11 tumor-associated peptides (TUMAPs), identified on human leukocyte antigen (HLA) surface receptors in primary human GBM tissue.

Experimental design:
Patients were HLA A*02 positive and had undergone tumor resection. Vaccination comprised 11 intradermal injections with IMA950 plus GM-CSF over a 24 week period, beginning 7-14 days prior to initiation of CRT (Cohort 1) or 7 days post CRT (Cohort 2). Safety was assessed according to NCI CTCAE Version 4.0 and TUMAP specific T cell immune responses determined. Secondary observations included progression-free survival (PFS), pre-treatment regulatory T-cell (Treg) levels and the effect of steroids on T-cell responses.

Results:
Forty five patients were recruited. Related adverse events included minor injection site reactions, rash, pruritus, fatigue, neutropenia and single cases of allergic reaction, anemia and anaphylaxis. Two patients experienced Grade 3 dose limiting toxicity of fatigue and anaphylaxis. Of 40 evaluable patients, 36 were TUMAP responders and 20 were multi-TUMAP responders, with no important differences between cohorts. No effect of pre-treatment Treg levels on IMA950 immunogenicity was observed and steroids did not affect TUMAP responses. PFS was 74% at 6 months and 31% at 9 months.

Conclusion:
IMA950 plus GM-CSF was well tolerated with the primary immunogenicity endpoint of observing multi-TUMAP responses in at least 30% of patients exceeded. Further development of IMA950 is encouraged.

Full text

A Cancer Research UK First Time in Human Phase I Trial of
IMA950 (Novel Multi-Peptide Therapeutic Vaccine) in Patients
with Newly Diagnosed Glioblastoma
Roy Rampling1, Sharon Peoples2, Paul J. Mulholland3, Allan James1, Omar Al-Salihi4,
Christopher J. Twelves5, Catherine McBain6, Sarah Jefferies7, Alan Jackson8, Willie
Stewart9, Juha Lindner10, Sarah Kutscher10, Norbert Hilf10, Lesley McGuigan11, Jane
Peters11, Karen Hill11, Oliver Schoor10, Harpreet Singh-Jasuja10, Sarah E. Halford11, and
James W.A. Ritchie11
1University of Glasgow, Beatson West of Scotland Cancer Centre, 1053 Great Western Road,
Glasgow, G12 0YN UK
2Edinburgh Centre for Neuro-Oncology, Western General Hospital, Edinburgh, UK
3Department of Oncology, University College London Hospitals, 1st Floor Central, 250 Euston
Road, London, NW1 2PG, UK
4Adult Neuro-Oncology, Southampton University Hospitals NHS Trust, Tremona Road,
Southampton, SO16 6YD, UK
5Cancer Research UK Clinical Centre, St James’s University Hospital, Leeds, LS9 7TF, UK
6The Christie NHS Foundation Trust, Wilmslow Road, Withington, Manchester, M20 4BX UK
7Cambridge Cancer Trials Centre, Oncology Clinical Trials, Addensbrooke’s Hospital, Hills Road,
Cambridge, CB2 0QQ, UK
8Wolfson Molecular Imaging Centre, University of Manchester, 27 Palatine Road, Manchester,
M20 3LJ, UK
9Department of Neuropathology, The Queen Elizabeth University Hospital, 1345 Govan Road,
Glasgow, G51 4TF, UK
10Immatics Biotechnologies GmbH, Paul-Ehrlich-Str. 15, 72076 Tübingen, Germany
11Cancer Research UK Centre for Drug Development, Angel Building, 407 St John Street,
London, EC1V 4AD, UK
Corresponding author: James W.A. Ritchie, Cancer Research UK Centre for Drug Development, Angel Building, 407 St John Street,
London, EC1V 4AD, UK; e-mail: james.ritchie@cancer.org.uk; Telephone: +44 1367 240373; FAX: +44 20 3357 3182.
Trial registration ID: NCT01222221
Conflicts of interest Statement: Norbert Hilf, Sarah Kutscher, Juha Lindner, Oliver Schoor and Harpreet Singh are current or past
employees of Immatics Biotechnologies. Sarah Kutscher, Norbert Hilf, Oliver Schoor and Harpreet Singh have stock ownership
interests in Immatics Biotechnologies. Sarah Kutscher, Norbert Hilf, Oliver Schoor, Harpreet Singh have intellectual property interests
in Immatics Biotechnologies. Sarah Kutscher, Norbert Hilf, Oliver Schoor and Harpreet Singh have received either travel,
accommodation or other expenses from Immatics Biotechnologies during the previous two years. Harpreet Singh has a leadership role
at Immatics Biotechnologies. Other authors disclosed no conflicts of interest.
Presented in abstract form at the European Society for Medical Oncology 2012 Congress, Vienna, Austria, September 28 to October 2,
2012; and European Society for Medical Oncology 2014 Congress, Madrid, Spain, September 26 to 30, 2014.
Europe PMC Funders Group
Author Manuscript
Clin Cancer Res. Author manuscript; available in PMC 2017 April 01.
Published in final edited form as:
Clin Cancer Res
. 2016 October 1; 22(19): 4776–4785. doi:10.1158/1078-0432.CCR-16-0506.
Europe PMC Funders Author Manuscripts Europe PMC Funders Author Manuscripts

Abstract
Purpose—To perform a two-cohort, phase 1 safety and immunogenicity study of IMA950 in
addition to standard chemo-radiotherapy (CRT) and adjuvant temozolomide in patients with newly
diagnosed glioblastoma (GBM). IMA950 is a novel GBM specific therapeutic vaccine containing
11 tumor-associated peptides (TUMAPs), identified on human leukocyte antigen (HLA) surface
receptors in primary human GBM tissue.
Experimental Design—Patients were HLA-A*02 positive and had undergone tumor resection.
Vaccination comprised 11 intradermal injections with IMA950 plus GM-CSF over a 24 week
period, beginning 7-14 days prior to initiation of CRT (Cohort 1) or 7 days post CRT (Cohort 2).
Safety was assessed according to NCI CTCAE Version 4.0 and TUMAP specific T-cell immune
responses determined. Secondary observations included progression-free survival (PFS), pre-
treatment regulatory T-cell (Treg) levels and the effect of steroids on T-cell responses.
Results—Forty five patients were recruited. Related adverse events included minor injection site
reactions, rash, pruritus, fatigue, neutropenia and single cases of allergic reaction, anemia and
anaphylaxis. Two patients experienced Grade 3 dose limiting toxicity of fatigue and anaphylaxis.
Of 40 evaluable patients, 36 were TUMAP responders and 20 were multi-TUMAP responders,
with no important differences between cohorts. No effect of pre-treatment Treg levels on IMA950
immunogenicity was observed and steroids did not affect TUMAP responses. PFS was 74% at 6
months and 31% at 9 months.
Conclusion—IMA950 plus GM-CSF was well tolerated with the primary immunogenicity
endpoint of observing multi-TUMAP responses in at least 30% of patients exceeded. Further
development of IMA950 is encouraged.
Keywords
IMA950; Phase I study; therapeutic cancer vaccine; glioblastoma; immunotherapy
Introduction
GBM, the most aggressive central nervous system tumor, develops from glial tissue of the
brain and spinal cord (1). Newly diagnosed GBM is an orphan disease with 100% mortality
and a median overall survival (OS) of only 14.6 months (2). Standard first-line therapy
comprises maximal safe tumor resection, followed by concomitant chemo-radiotherapy
(radiotherapy plus daily temozolomide; CRT) and six 28-day cycles of adjuvant
temozolomide (TMZ) (2). Although the incidence is relatively low, around 3 to 4 cases per
100,000 population (3), GBM affects patients of all ages and there is a large unmet medical
need for improved first-line therapy. Furthermore, there is evidence to suggest that the
overall incidence of GBM is rising over time and will continue to increase in an ageing
population (4, 5).
IMA950 is an immunotherapeutic multiple-peptide vaccine specifically developed to treat
GBM (6). It contains 11 tumor-associated peptides (TUMAPs) that are presented by a
majority of GBMs on human leukocyte antigen (HLA) surface receptors. IMA950 is
designed to trigger the immune system by activation of TUMAP-specific cytotoxic T cells.
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Once activated, these cells are postulated to find and destroy malignant tumor cells
presenting the cognate TUMAPs. By vaccinating with 11 TUMAPs simultaneously there is
an increased probability that a multi-clonal, broad yet highly specific T-cell response can be
mounted against tumor cells thus hindering potential tumor escape mechanisms.
The primary objectives of this first time in human study were to assess the safety, tolerability
and immunogenicity of IMA950 plus GM-CSF given alongside standard therapy in newly
diagnosed GBM patients.
Patients and Methods
Patients
Eligible patients had histologically or cytologically proven GBM, an operable tumor which
had already been maximally resected, were at least 18 years of age, human leukocyte antigen
(HLA) A*02 positive and hepatitis B core antigen seronegative; had a World Health
Organization (WHO) performance status 0 or 1, a life expectancy of at least 30 weeks and
were expected to complete standard CRT and six 28 day cycles of adjuvant TMZ. Key
exclusion criteria included: receipt of any prior GBM treatment apart from surgery,
vaccination within 2 weeks or having taken dexamethasone at a dose >4 mg/day within 7
days prior to the first IMA950 plus GM-CSF vaccination, a history of serious cardiac or
autoimmune disease or any condition which might interfere with the patient’s ability to
generate an immune response. This study was conducted in accordance with the principles
of International Conference on Harmonisation (ICH) Good Clinical Practice (GCP), the
requirements of the UK Clinical Trials regulations (SI 2004/1031 and SI 2006/1928), and
the Declaration of Helsinki. The study protocol, patient information sheet and informed
consent form were approved by the Sponsor’s Central Institutional Review Board, and the
appropriate Research Ethics Committee prior to study conduct. After a full explanation of
the study protocol, written informed consent was obtained from all patients before being
enrolled.
IMA950 Vaccine
IMA950 is a novel multi-peptide GBM specific vaccine comprising 11 HLA binding
TUMAPs and one viral marker peptide, identified on HLA surface receptors in primary
human GBM tissue, as described previously (6). Supplementary Table S1 gives an overview
of the TUMAP source antigens and their respective expression levels found in primary GBM
tumor samples. Selected TUMAPs are designed to activate TUMAP-specific CD8+
cytotoxic and CD4+ helper T lymphocytes, which then recognize cognate TUMAPs
presented by GBM tumor cells and effect a targeted immune response. Nine of the 11
TUMAPs were selected on the basis of their functional relevance, association with the
human leukocyte antigen HLA-A*02, over-expression in GBM and proven immunogenicity
using in vitro T-cell assays. The other two TUMAPs contained in IMA950 are both HLA
class II-binding peptides designated IMA-BIR-002 and IMA-MET-005. IMA-BIR-002 has
the capacity to activate CD4+ helper T cells (7) and potentially cytotoxic T lymphocytes
(CTLs). IMA-MET-005 contains a known HLA class I epitope, which was elongated based
on the natural sequence of c-Met (known oncogene and potential marker of GBM stem cells
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(8), with the capacity to activate helper T cells (9) and, after processing, CTLs). An
additional non-TUMAP (IMA-HBV-001) was included in IMA950 derived from Hepatitis B
virus (HBV) core antigen, to act as a positive control from a “non-self” antigen in cases
where no vaccine-induced T-cell responses to TUMAPs from “self” antigens are observed.
Study Design and Treatment
Vaccination comprised fixed doses of recombinant granulocyte macrophage-colony
stimulating factor (GM-CSF; 75 μg), a commonly used immunomodulator (10), followed by
IMA950 (4.96 mg, 413 μg each peptide) injected intradermally (i.d.) at 11 time points over a
24 week period. All patients received the same vaccination schedule comprising an
“Induction Phase” (VIP) of six intensive vaccinations (V1-V6), followed by a "Maintenance
Phase" (VMP) of five vaccinations (V7-V11) over a longer period. Forty five patients with
newly diagnosed GBM were entered into one of two Cohorts that differed by virtue of the
first vaccination given at different time points alongside standard therapy (rationale for
recruiting at least 20 patients per cohort is given in Supplementary Table S2). In Cohort 1,
the VIP started 7 to 14 days before the scheduled onset of CRT to ensure that at least the
first three vaccinations (Days 1, 2, 3) were administered prior to the start of CRT. In Cohort
2, the VIP started a minimum of 7 days after the final dose of CRT and 28 days (+7 days)
prior to the first scheduled dose of adjuvant TMZ. This ensured that all six vaccinations in
the VIP were administered at least a week after the end of immunosuppressive CRT and
completed a week prior to the start of adjuvant TMZ. Three safety observation periods of 21
days were included after 1, 3 and 6 patients had completed 21 days of treatment prior to
opening to general recruitment. CRT comprised 54 to 60 Gray in 30 daily fractions over 6
weeks with concomitant daily TMZ, 75 mg/m2 throughout. Adjuvant TMZ, 150-200 mg/m2
for 5 days began 35 (+/-7 days) following the last fraction of radiotherapy, repeated every 28
days for a total of 6 cycles. See Supplementary Fig. S1 for a detailed overview of the
treatment and assessment schedule.
Patient Monitoring and Assessment
The primary study endpoint of safety and tolerability was assessed according to National
Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version
4.0. Disease was assessed using MacDonald criteria (11) with the secondary endpoint of
progression free survival evaluated at 6 (PFS-6) and 9 months (PFS-9) from date of surgery.
Any clinical complete (CR) or partial response (PR) to therapy was confirmed by an
independent neuro-oncologist and radiologist. Although not an endpoint of the study,
survival data was collected for two years after the final patient had received their first
vaccination. The cut-off date for analysis was February 18, 2015.
Pharmacodynamic Analysis
A co-primary endpoint was determining the number of patients showing patient individual
T-cell responses directed against TUMAPs contained in IMA950 at one or more post-
vaccination time points, as determined by HLA multimer analysis (12, 13). Individual
patient peripheral blood mononuclear cell (PBMC) samples were pooled in order to ensure
sufficient viable PBMCs for multimer analysis as follows: “Pre-vaccination” (PBMC
samples 1 and 2), “post-vaccination 1” (PBMC samples 3 and 4), “post-vaccination 2”
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(PBMC samples 5 and 6) and “post-vaccination 3” (samples 7 and 8). See Supplementary
Fig. S1 for further details. Tetramer staining for each TUMAP and control antigens were
performed after an in vitro sensitization as described previously (13). Exemplary gating is
shown in Supplementary Fig. S2. A positive vaccine-induced multimer CD8 T-cell response
for any specific post-vaccination time point of a given antigen and patient was assigned if
the following criteria were met: an above threshold immune response (assessed by five
independent, trained and blinded jurors and according to Association for Cancer
Immunotherapy recommendations (14)) and an at least four-fold higher frequency of
multimer positive CD8 T cells (normalized to total CD8 T cells) compared to the respective
pre-vaccination time point. Based on prior clinical experience, at the time of study inception,
with similar multi-peptide vaccines (13), study success criteria were defined as either ≥ 30%
multi-TUMAP response or > 60% single TUMAP response in the study population. Further
development would be recommended if either criterion was met. Secondary outcome
measures included Treg levels (defined as CD3+CD4+CD8-CD25highCD127lowFoxp3+
lymphocytes (15)) pre- and post-vaccination, and correlation of steroid dose with observed
T-cell responses. Research analysis examined the kinetics of TUMAP immunogenicity,
effect of O6-Methylguanine DNA methyltransferase (MGMT) promoter methylation status
on PFS and exploring the possible effects of vaccination on observed disease pseudo-
progression and pseudo-regression measured using a standardized diffusion-weighted (DWI)
and perfusion-weighted (PWI) magnetic resonance imaging (MRI) protocol. Pseudo-
progression was defined as an apparent increase in the enhancing tumor (>25%) on an early
reference scan followed by a reduction in subsequent scans (assessed at Week 25 onwards),
with no associated clinical deterioration. Pseudo-regression was assessed using an inverse
definition. It was recommended that patients continue on therapy until the true clinical
diagnosis was clarified. Although this design pre-dated that of recently published guidance,
suggesting that patients continue the immunotherapy regimen for 3 months prior to PD
confirmation (16), it is generally in line with these recommendations.
Statistical Analysis
For the pharmacodynamic analysis, several different methods were used to calculate
statistical significance depending on the type of data being examined. All statistical analysis
was performed using Prism version 6.02 software (GraphPad Software Inc., La Jolla,
California, USA). Two-tailed non-parametric Mann-Whitney test was used to determine
differences between independent groups under examination. This included, for example, the
number of vaccine induced TUMAP responses per patient between Cohorts and frequency
of Treg as a percentage of total lymphocytes for a given patient compared between Cohorts.
Fisher’s exact test was used to analyze contingency tables. This included a comparison of
the proportion of patients showing a TUMAP response between Cohorts. Non-parametric
Spearman’s rank correlation test was used to analyze dependence between two variables
such as immune responses and regulatory T cell levels.
The Kaplan-Meier method was used to generate survival curves and estimate OS rates. Log
rank test was used to compare the survival distributions between groups of patients that
included censored data.
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Statistical analysis of imaging parameters was performed using a one-way ANOVA analysis
with post hoc intergroup analysis using Tukey’s test, due to a significant number of datasets
being unavailable for analysis.
Results
Patient Demographics
Table 1 provides an overview of patient demographics. Of 138 patients screened, 53% were
HLA-A*02 positive, which is in the expected range for a United Kingdom population (17).
Reasons for non-entry of 26 HLA-A*02 patients is given in Supplementary Table S3. Forty
five patients were recruited into the study; 22 in Cohort 1 and 23 in Cohort 2. Forty patients
were immune evaluable, with 39 evaluable for clinical activity assessment. This discrepancy
is a result of two patients being lost for follow up between blood sample 6 and week 25 scan
(see Supplementary Fig. S1), including one patient that was immune evaluable. The overall
median age was 53 years (range 20-75 years) with no meaningful difference between
cohorts. All patients had WHO performance status (PS) 0 or 1 at recruitment. A larger
proportion of patients in Cohort 2 (65%) had a PS of 1 compared to Cohort 1 (27%), most
likely due to Cohort 2 patients having undergone treatment with CRT. As expected, the
lymphocyte count on patient entry was lower in Cohort 2 (0.80x109/L) compared to Cohort
1 (1.49x109/L) reflecting the effect of concomitant TMZ in the former. Of the 38 patients
evaluable for MGMT promoter methylation testing, 11 (29%) were positive for methylated
promoter, 8 of 19 (42%) in Cohort 1 compared to 3 of 19 (16%) in Cohort 2.
Safety
All patients received at least one vaccination and were evaluated for safety (see Table 2 for
the most commonly reported adverse events (AEs), regardless of causality). Injection site
reaction (ISR) was the most frequent AE, and most common study drug related AE with 81
instances reported in 26 patients (12/22 patients in Cohort 1 and 14/23 patients in Cohort 2).
The majority of ISRs were grade 1 (24 out of 26 patients) with only two instances of grade 2
events. Thirty one patients experienced at least one serious adverse event (SAE), one of
which was a death unrelated to the study drug. The most frequently reported SAEs were
seizure in 8 patients followed by thromboembolic events in 6 patients, none was study drug
related. Investigators considered 4 SAEs to be related to the study drug including two cases
of grade 4 neutrophil count decrease and one case each of grade 3 fatigue and anaphylaxis.
The related SAEs of anaphylaxis and fatigue were both considered dose limiting toxicities.
There were no unexpected differences in the safety profiles observed in the two cohorts.
Pharmacodynamics
Thirty six of 40 immune evaluable patients (90%) were TUMAP responders, with 20 (50%)
responding to more than one TUMAP (Fig. 1A). The pre-defined primary immunologic
endpoint for recommending further development (≥60% single or ≥30% multi TUMAP
responders) was therefore reached for the total immune evaluable study population and each
of the two individual study cohorts. In Cohort 1, 9/19 (47%) evaluable patients responded to
multiple TUMAPs, with a further 9 (47%) responding to a single TUMAP. Similarly, in
Cohort 2, 11/21 (52%) evaluable patients had multiple TUMAP responses and a further 7
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(33%) had a single response. Although the number of vaccine induced responses per patient
in Cohort 2 appeared to be greater than in Cohort 1 (an arithmetic mean of 2.2 in Cohort 2
versus 1.6 in Cohort 1), this was not statistically significant (p=0.3; Mann Whitney test; Fig.
1B). Immune response kinetics showed a predominant onset of vaccine-induced TUMAP
responses in the post-vaccination 1 sample PBMC pool, with 47 (61%) being detected at this
time point (Fig. 2A). This was also true for each cohort. In addition, 24 out of 77 (31%) of
vaccine-induced TUMAP responses were already detectable pre-vaccination and were
boosted at least four-fold by administration of IMA950 plus GM-CSF (data not shown). The
majority of vaccine-induced TUMAP responses were detectable at one post-vaccination
assay time point only (61%, 52/77 immune responses; Fig. 2A) and were of relatively low
magnitude (see Supplementary Fig. S3 for exemplary data). The proportion of vaccine
induced TUMAP responses detected at only one post-vaccination assay time point was
significantly higher (p=0.025; Fisher’s exact test) in Cohort 1 (25/30 immune responses;
83%) than in Cohort 2 (27/47 immune responses; 57%) (Fig. 2B). No apparent differences in
TUMAP responses were noted between patients who were and were not receiving
concomitant steroid treatment (data not shown).
Twenty five immune evaluable patients (63%) responded to the “non-self” viral antigen,
IMA-HBV-001 (13) and was by trend, associated with the number of vaccine-induced
TUMAP responses (p=0.117 by Wilcoxon test; data not shown). There was also a trend for
the proportion of IMA-HBV-001 responders to be enriched within the multi-TUMAP
responder fraction of patients (p=0.191 by Fisher’s exact test; data not shown).
There was no correlation between pre-treatment Treg levels and number of vaccine-induced
TUMAP responses overall (Fig. 3A) or within either cohort of patients (Fig 3B and C). A
comparative analysis of study cohorts revealed that pre-treatment Treg levels normalized to
lymphocytes were significantly increased (p=0.0003 by Wilcoxon test) in Cohort 2
compared to Cohort 1 (Fig. 3D).
In order to explore possible effects of vaccination on observed pseudo-progression and
pseudo-regression of disease, DWI and PWI was performed alongside standard gadolinium
MRI scans. Cohort 1 patients showed increases in apparent diffusional coefficient (p<0.05),
following CRT (see Supplementary Fig. S4). Over the same period, PWI parameters showed
a trend (albeit not statistically significance) towards increased T1 values, contrast transfer
coefficient (Ktrans) and total enhancing volume (
ve
) with an associated decrease in plasma
volume (
vp
) between scans 1 and 2 (data not shown).
Clinical Activity
Twenty nine of 39 evaluable patients were progression free at 6 months (PFS-6 of 74.4%)
with 12 continuing to be progression free at 9 months (PFS-9 of 30.8%). Stable disease (SD)
was confirmed for 11 evaluable patients (28.2%) at Week 40. One patient with residual
disease at baseline had a partial response (PR) at Week 40, with tumor size decreasing from
357 mm2 at baseline to 25 mm2 at week 17, being maintained until they went off study. Four
patients with SD and the patient with PR at Week 40 had MGMT promoter methylation
(5/11 patients with a methylated MGMT promoter; 45.5%). Five other patients with SD at
Week 40 had unmethylated MGMT promoters (5/27 patients with an unmethylated MGMT
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promoter; 18.5%). Eleven patients out of an evaluable 38 (29%) had a methylated MGMT
promoter, which conferred a significant survival advantage (28.3 versus 14.8 months;
p=0.025 using Log-rank test; data not shown).
As of the cutoff date (18-Feb-15), median OS for the study was 15.3 months (Fig. 4A) with
no significant differences between the cohorts or those patients that responded to multiple
TUMAPs compared to those that did not respond or to one TUMAP only (Fig. 4B).
Interestingly, patients experiencing one or more ISRs had a significantly improved (p =
0.0001; hazard ratio 0.33) median OS of 26.7 months compared to 13.2 months for those
that did not (Fig. 4C). The median age of patients in the ISR group was significantly lower
than that of the non-ISR (47 versus 57 years respectively; p = 0.023 by Mann Whitney test).
Imaging parameters in patients displaying ISRs showed no significant difference. However
in Cohort 2 ISR was associated with lower Ktrans (p <0.05),
vp
(p<0.01),
ve
(p<0.05) and
rate constant Kep (p<0.05) values at baseline.
Discussion
In the majority of treated GBM patients, IMA950 produced antigen specific peripheral
CD8+ T-cell immune responses to the TUMAPs contained within the vaccine, with a
relatively benign drug related toxicity profile comprising mainly minor injection site
reactions. The two cohort study design was used to help define the most biologically
effective and clinically feasible administration schedule of IMA950 for subsequent
development as determined by the level of vaccine induced TUMAP specific immune
responses for each schedule. However, it does not allow direct comparison of clinical
efficacy between cohorts since recruitment was not randomized nor was the trial
prospectively powered to make such a comparison. Both cohorts presented challenges that
had the potential to interfere with successful vaccination and the mounting of a measurable
TUMAP specific immune response. In Cohort 1, there was a risk that CRT could be
immunosuppressive (18, 19) and interfere with the induction and maintenance of TUMAP
specific CD8+ T cells. Whereas in Cohort 2 there was the possibility that following
completion of CRT, patient lymphocyte counts would be depleted and have lost the ability to
mount a detectable immune response to IMA950. Indeed, immune data showed that Cohort
1 patients had a decreased detection rate of vaccine induced TUMAP responses at later time
points (Fig. 2), suggesting that CRT may interfere with the induction and maintenance of
antigen specific CD8+ T cells. The greater number and improved durability of TUMAP
responses in Cohort 2 suggests that lymphocyte depletion caused by CRT is either
insufficient to hinder induction of antigen specific CD8+ T cells or can be recovered
sufficiently rapidly to support their expansion.
Treg are a potent immunosuppressive cell population (20) that may interfere with the
immunogenicity of cancer vaccines (21). Given this, an additional key biological endpoint of
this study was to explore the effect of pre-treatment Treg levels on the immunogenicity of
IMA950. There was no correlation between pre-treatment Treg levels (relative to the overall
lymphocyte population) and the number of vaccine induced TUMAP responses for the
overall group of immune evaluable study patients. This result is similar to previous reports in
other GBM vaccine studies (22, 23). There was a significant increase in the Treg levels at the
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start of vaccinations in Cohort 2 compared to Cohort 1, likely indicating a relative increase
of Treg compared to other lymphocyte subpopulations as a result of the preceding CRT (24).
The importance of this finding is unclear given that there were more vaccine-induced
immune responses in Cohort 2.
The overall number of immune evaluable patients responding to multiple TUMAPs in this
study (50%) exceeded that demonstrated for other similar vaccine products (13) such as
IMA901, which had a multi-TUMAP response rate of 26%. In contrast to that found with
IMA901, there was no apparent correlation between the number of TUMAP responses and
improved survival (Fig. 4B). However, there are key differences between this study and that
of IMA901. IMA901 comprises different TUMAPs, selected specifically for the treatment of
renal cell carcinoma (RCC) patients and the IMA901 study was conducted in the absence of
potentially confounding standard of care therapy. Low dose cyclophosphamide (shown to
decrease the number and function of Treg (25, 26)) was also used alongside GM-CSF to
further enhance immune response potential. In addition, RCC is known to be an immune-
responsive tumor type (27), whereas immunotherapy for GBM is still in its infancy. Indeed,
cancer vaccine immunotherapy strategies for GBM patients require considerable refinement
due to the challenges posed by immune resistance and suppression in this tumor type (28).
Multiple immunosuppressive mechanisms are likely to be important in GBM including,
enhanced secretion of immunosuppressive factors after exposure to standard therapy (29),
induction of tumor infiltrating lymphocytes and Treg activity (30), as well as immune
checkpoint pathways such as PD-1/PD-L1 and CTLA-4 (31, 32).
The aim of administering adjuvant(s) alongside therapeutic vaccines is to attempt to
augment immune response and overcome immune suppression by either: moving the
immune response toward Th1 or Th2 immunity, activating innate immunity or to serve as a
local repository for prolonged antigen release and protection from degradation. In this study
we utilized GM-CSF as an adjuvant based on the principle that it should enhance effective
priming of T-cell responses (33, 34) and the fact that it had been successfully applied in late
stage clinical trials (35). There is evidence to suggest that in some circumstances at least,
GM-CSF may not significantly enhance immune responses and may even be detrimental
(36). Even so, an earlier meta-analysis of published trials suggests that low-dose GM-CSF
(40-80 μg for 1-5 days) given s.c. or i.d. at the site of vaccination enhances the cellular
immune response, while high-dose, systemic treatment (>=100 μg) does not increase the
efficacy of a peptide vaccine due to expansion of immune-inhibiting MDSCs (10). Based on
this evidence, we opted for a fixed dose of 75 μg GM-CSF given i.d. prior to vaccination
with IMA950. In light of the relatively low magnitude and transient immune responses,
enhancement of the vaccination regimen, including selection of the most effective adjuvant
partner(s), is necessary; for example by using alternate or additional adjuvants such as
locally applied poly-ICLC (37), imiquimod (38) or systemically administering CD40 ligand
(39) or cyclophosphamide (40). Combining cancer vaccines such as IMA950 with immune
checkpoint inhibitors such as anti-PD1/PD-L1 or anti-CTLA4 antibodies should also be
expected to enhance anti-tumor immune responses. This is based on the rationale that
overcoming local immune suppression and T cell anergy by checkpoint blockade can be
limited by the specificity/size of the pre-existing T cell population and the fact that some
tumors are relatively non-immunogenic. Indeed, preclinical and clinical data is beginning to
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emerge demonstrating that the anti-tumor activity of immune checkpoint blockade can be
enhanced by vaccination (41, 42).
The observation that patients experiencing one or more ISRs had improved survival and
were generally of younger age, suggest that ISR may be a prognostic marker for a patient
population with an inherently healthier immune system (43). This is supported by the
significantly different imaging features in Cohort 2 patients experiencing ISRs whose tumors
showed less vascularity and reduced angiogenesis associated vascular permeability.
Although this was an unplanned and retrospective analysis, a contribution of the vaccine to
patient survival for those with a more vigorous immune system cannot be ruled out and
could be investigated in future randomized studies that might include a non-specific
immunogen. In addition, methylation of MGMT promoter conferred a survival advantage for
GBM patients, as previously reported (44).
A key factor that will need to be considered during the future development of IMA950 and
therapeutic cancer vaccines more generally is the need to continue vaccination even after the
disease appears to be progressing. Unlike conventional cancer chemotherapy, the effect of
cancer immunotherapies is not directly on the disease but rather on the immune system
which leads to a cellular immune response followed by tumoricidal biological activity and
potentially improved patient survival (45). This can lead to non-typical patient survival
curves and misinterpretation of study results. Given this, chronic vaccination beyond disease
progression, and potentially during subsequent therapy, will need to be carefully planned as
part of future positioning alongside other therapy for the treatment of GBM.
IMA-HBV-001 was also included in the IMA950 vaccine to act as a positive control in cases
where no vaccine-induced T cell responses to TUMAPs from “self” antigens are observed.
There was a trend (albeit not reaching statistical significance) for patients mounting an
immune response toward IMA-HBV-001 also to respond to one or more TUMAP,
supporting its use as a general immunogenicity marker. However these findings also suggest
that IMA-HBV-001 has limited use as an independent control peptide for association
analysis.
Successful development of effective therapeutic vaccines for cancer has proven to be
particularly challenging. In the context of GBM, the most advanced therapeutic vaccine
approach was that of rindopepimut (CDX-110) which consists a single 14-mer peptide
derived from epidermal growth factor receptor variant III deletion mutation (EGFRvIII)
(46). Results from a Phase II single arm study of rindopepimut, given to newly diagnosed
EGFRvIII+ GBM patients post-CRT in combination with adjuvant TMZ, demonstrated a
median OS of 21.8 months, an increase in anti-EGFRvIII antibody titer and clearance of
EGFRvIII from the majority of analyzed post-treatment tumors (47). Even so, the resulting
pivotal, double-blind, randomized, Phase III trial using the same schedule and setting was
terminated at a planned interim analysis due to emergent data indicating that the study would
not reach statistical significance for the primary OS endpoint (48). It is currently unclear as
to why the study failed to meet the primary endpoint, albeit a median OS of 21.1 months
was reported for the placebo treated group (versus 20.4 months for vaccinated), well above
the expected median of approximately 16 months, which may have confounded the data. A
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previous report suggests that GBM patients taking part in US based Phase II trials have
significantly longer survival compared to historical data (49). The authors speculate that this
may be due to the novel agent being tested or advances in standard of care. If the latter is
correct, the apparent improvement in survival found in the Phase II rindopepimut study may
have lead to an overly optimistic prediction of clinical benefit and subsequent failure of the
Phase III trial. It is also possible that the reported loss of EGFRvIII from tumors during the
vaccination period may have led to escape from immune surveillance, an issue that the
IMA950 vaccine attempts to address by simultaneous targeting of 11 different antigens
(TUMAPs). Nevertheless, even though the study reported here clearly met predefined
immune response success criteria, further clinical optimization should precede transition of
IMA950 into the next phase of clinical development. This should include selection of the
most appropriate adjuvant(s) and gaining a deeper understanding of how best to combine
IMA950 with other immunotherapies, such as immune checkpoint inhibitors, in order to
maximize the magnitude of immune response, as well as gaining a better understanding as to
the optimal position and schedule of the vaccine relative to the current standard of care.
Supplementary Material
Refer to Web version on PubMed Central for supplementary material.
Acknowledgments
Funding: This work was supported by grant C222/A11422 from Cancer Research UK. This work was also
managed and sponsored by the Cancer Research UK Centre for Drug Development. Immatics Biotechnologies
provided pharmacodynamic assay support and supplied IMA950 for this study.
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Statement of Translational Relevance
Survival rates for patients with glioblastoma (GBM) are abysmal, with median overall
survival of approximately 15 months. Immunotherapy of GBM is a promising area of
investigation, although challenges around identification of novel and immunogenic target
antigens exist. IMA950 is a GBM specific vaccine comprising 11 tumor-associated
peptides (TUMAPs) developed to address this challenge. We have performed a phase 1
safety and immunogenicity study in newly diagnosed GBM patients using IMA950 plus
GM-CSF alongside standard of care chemo-radiotherapy. Our results demonstrate that
IMA950 is well tolerated with 90% of patients having a CD8+ T-cell immune response to
at least one TUMAP, with 50% responding to two or more TUMAPs. No effect of pre-
treatment regulatory T-cell levels on IMA950 immunogenicity was found and steroids did
not appear to affect immune responses to the TUMAPs. This data provides evidence to
support further development and optimization of IMA950 together with other
immunotherapies for GBM.
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Figure 1. Primary Immune Response Summary.
(A) Further development is based on: * >60% of patients being single or f †30% of patients
being multi-TUMAP responders. (B) The number of vaccine-induced TUMAP responses is
shown for the overall immune evaluable patient population (n=40) as well as for study
cohorts. Black lines indicate mean values. For statistical analysis the Mann-Whitney test was
used.
Abbreviations: HBV, hepatitis B virus-derived vaccinated marker peptide; TUMAP, tumor
associated peptide; VI, vaccine induced.
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Figure 2. Onset and sustainability of vaccine induced immune responses.
(A) Onset (first appearance) of vaccine-induced immune responses to IMA950 TUMAPs
(n=77 total detected vaccine-induced responses in n=40 immune evaluable patients). (B) The
percentage of vaccine-induced responses to IMA950 TUMAPs with detection at one, two or
three post-vaccination assay time points. p-values were calculated using the Fisher’s exact
test (only significant results are shown).
Abbreviations: TUMAP, tumor associated peptide; VI, vaccine induced.
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Figure 3. Correlation of pre-treatment levels of regulatory T cells with vaccine-induced immune
responses to IMA950 TUMAPs.
Treg (CD4+/CD25hi/CD127lo/FoxP3+) levels, normalized to lymphocytes, at V1 were
analyzed in correlation with vaccine-induced CD8 T-cell responses to IMA950 TUMAPs in
(A) all immune evaluable patients with n=40, (B) study Cohort 1 with n=19 and (C) study
Cohort 2 with n=21. Correlation coefficients and p-values, calculated using Spearman’s
correlation, are indicated on each graph. (D) Cohort comparison of pre-treatment Treg levels
on the first vaccination day for immune evaluable patients. For statistical analysis the Mann-
Whitney test was used.
Abbreviations: Treg, regulatory T cells; TUMAP, tumor associated peptide; V1, vaccination
1.
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Figure 4. Overall survival from date of surgery for different patient sub-sets.
A) Median OS was 15.3 months for all patients (n = 44), 14.4 months for patients in Cohort
1 (n =22) and 15.7 months for patients in Cohort 2 (n = 22). There was no significant
difference between each of the cohorts (p = 0.63, Log-rank test); one patient was lost for
follow up in Cohort 2 and excluded from survival analysis. B) Relationship between survival
and TUMAP response. Only patients that were immune evaluable were included in the
analysis. Log-rank test was used to calculate significance between the two different patient
populations. C) Relationship between overall survival and injection site reaction. One patient
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was lost to survival follow up and is excluded from the analysis. Log-rank test was used to
calculate significance and hazard ratio. Median age of patients in the ISR group was
significantly lower than that of the non-ISR (47 versus 57 years respectively; p = 0.023 by
Mann Whitney test).
Abbreviations: HR, hazard ratio; ISR, injection site reaction; TUMAP, tumor associated
peptide; y, years.
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Table 1
Patients’ Baseline Characteristics
Characteristic Cohort 1 Cohort 2 Overall
Age, years
Median 54 49 53
Range 21 – 75 20 – 68 20 – 75
Sex, No. (%)
Male 15 (68%) 15 (65%) 30 (67%)
Female 7 (32%) 8 (35%) 15 (33%)
Total 22 23 45
WHO performance status, No. (%)
0 16 (73%) 8 (35%) 24 (53%)
1 6 (27%) 15 (65%) 21 (47%)
MGMT methylation status, No. (%
†
)
Methylated 8 (42%) 3 (16%) 11 (29%)
Unmethylated 11 (58%) 16 (84%) 27 (71%)
Unavailable 3 4 7
Lymphocyte count, x109/L
Median 1.49
*
0.80
*
1.12
Range 0.88 – 2.50 0.35 – 1.91 0.35 – 2.50
Concomitant steroid use, No. (%)
Yes 16 (73%) 17 (74%) 43 (73%)
Entry concomitant steroid dose, mg
Median 2.0 1.5 2.0
Range 0 – 4.0 0 – 4.0 0 – 4.0
Abbreviations: WHO, World Health Organization; MGMT, O6-Methylguanine DNA methyltransferase.
†
Percentages calculated excluding those patients whose MGMT methylation status was unavailable.
*
Significantly different lymphocyte counts between the two cohorts; p < 0.0001, two-tailed Man-Whitney test.
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Table 2
Most Common Adverse Events Occurring in >20% Patients (regardless of causality)
Grade, No.
Symptom*1 234Total No. (% pts)
Nausea 21 6 0 0 27 (60%)
Injection Site Reaction 24 2 0 0 26 (58%)
Fatigue 16 5 4 0 25 (56%)
Headache 20 2 0 0 22 (49%)
Vomiting 16 4 1 0 21 (47%)
Alopecia 8 8 0 0 16 (36%)
Dizziness 11 3 0 0 14 (31%)
Seizure 4 4 3 2 13 (29%)
Cough 9 2 0 0 11 (24%)
Abbreviations: pts, patients.
*
Patients may have experienced multiple AEs of the same type.
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