RCS - PureTech Health PLC - PRTC's Gallop: Positive Ph1 Topline MDS & AML Data

Puretech HealthAnnouncement

22/04/2026 12:00

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RNS Number : 4332B  PureTech Health PLC  22 April 2026

22 April 2026

PureTech Health plc

 

PureTech Reports Positive Topline Data from Phase 1b Trial of LYT-200 in
Relapsed/Refractory (R/R) High-Risk (HR) Myelodysplastic Syndrome (MDS) and
R/R Acute Myeloid Leukemia (AML)

 

Phase 1b dataset with LYT-200 demonstrates complete responses and favorable
tolerability across both R/R HR-MDS and R/R AML

 

PureTech's Founded Entity, Gallop Oncology, to advance LYT-200 first in R/R
HR-MDS, with continued development planned in R/R AML

 

Company plans to engage with the U.S. Food and Drug Administration to discuss
the design of a subsequent trial in R/R HR-MDS that has the potential to
support registration

 

PureTech Health plc (https://puretechhealth.com/)  (Nasdaq: PRTC, LSE: PRTC)
("PureTech" or the "Company"), a hub-and-spoke biotherapeutics company
dedicated to giving life to science and transforming innovation into value,
today announced positive topline data from the completed Phase 1b clinical
trial of LYT-200, a first-in-class, fully human anti-galectin-9 monoclonal
antibody, in heavily pretreated patients with relapsed/refractory (R/R)
high-risk (HR) myelodysplastic syndrome (MDS) and R/R acute myeloid leukemia
(AML). Based on the results, PureTech's Founded Entity, Gallop Oncology, has
selected a recommended Phase 2 dose (RP2D) and intends to engage with the U.S.
Food and Drug Administration (FDA) to discuss the design of a subsequent trial
that could potentially support registration of LYT-200 in R/R HR-MDS.

 

"The data from the completed Phase 1b trial highlight the potential for
LYT-200 to offer a differentiated treatment approach across a range of myeloid
hematological malignancies," said Aleksandra Filipovic, M.D., Ph.D., Head of
Oncology at PureTech and Chief Medical Officer of Gallop Oncology. "Across
patients with R/R HR-MDS and R/R AML, treatment with LYT-200 resulted in deep
responses with an exceptionally favorable safety profile. Importantly, the
data in R/R HR-MDS were particularly compelling and support prioritizing this
indication, especially given the significant unmet need and lack of successful
innovation to help these patients. We intend to engage with the FDA to discuss
the design of a subsequent trial in R/R HR-MDS, as our goal is to accelerate
delivery of this promising first-in-class therapy to patients while also
laying the foundation for broader clinical development, including in AML."

 

The completed Phase 1b trial (NCT05829226), conducted across nine U.S. sites,
evaluated LYT-200 both as a monotherapy and in combination regimens in two
heavily pretreated patient populations.

The study included dose escalation of monotherapy LYT-200, followed by dose
escalation of LYT-200 in combination with a hypomethylating agent (HMA;
azacitidine or decitabine) in patients with R/R HR-MDS and with venetoclax
(VEN) and an HMA in R/R AML.

 

"The safety profile, combinatorial potential, and level of clinical activity
observed with LYT-200 in this Phase 1b study across both R/R HR-MDS and R/R
AML is very encouraging, particularly given the number of prior lines of
treatment and the risk profile in the populations studied," said Amir T.
Fathi, M.D., Program Director of the Center for Leukemia at the Mass General
Brigham Cancer Institute and Professor of Medicine at Harvard Medical School.
"In R/R high-risk MDS, where treatment options are extremely limited and
outcomes are poor, the findings are particularly notable. In this context, the
potential to achieve clinical responses without added toxicity would represent
a meaningful advance in the MDS treatment landscape and warrants continued
clinical development."

 

"The results from this Phase 1b trial provide a strong foundation for the next
stage of development of LYT-200," said Eric Elenko, Ph.D., President and
Co-founder of PureTech and Acting Chief Executive Officer of Gallop Oncology.
"Our decision to prioritize relapsed/refractory high-risk MDS reflects a
focused and disciplined approach, grounded in both the data generated to date
and the potential to address a tremendous patient need. We intend to engage
with the FDA to discuss a subsequent trial design with the potential to
support registration, while continuing to evaluate the broader potential of
LYT-200."

 

TOPLINE SAFETY DATA

LYT-200 demonstrated a favorable and consistent safety profile across all
cohorts and dose levels studied (N=101), with no dose-limiting toxicities,
infusion-related reactions, LYT-200 dose reductions, or LYT-200-related
serious adverse events (AEs), discontinuations, or deaths. Importantly, no
overlapping or additive toxicities were observed when LYT-200 was combined
with an HMA or VEN/HMA.

 

Six patients at one study site reported experiencing
hematology/chemistry-related Grade 3 or 4 AEs attributed as possibly related
or related to LYT-200 in the combination arm at the RP2D dose. The reported
AEs consisted of decreased levels of platelets, white blood cells, and
neutrophils that were below the lower limit of normal physiological levels.
The blood count deficits for some of the relevant patients were present at
baseline prior to the administration of LYT-200 and are common occurrences in
patients due to the underlying advanced MDS/AML, as well as in those receiving
VEN/HMA treatment. No other sites reported Grade 3 or greater AEs related to
LYT-200 treatment.

 

TOPLINE EFFICACY DATA

Treatment with LYT-200 in combination with an HMA in R/R HR-MDS patients and
VEN/HMA in R/R AML patients demonstrated robust antileukemic activity,
including complete responses, bridging to transplant, and durable clinical
benefit. The data also provided important insights into the contribution of
LYT-200 within combination regimens.

 

R/R HR-MDS

Across all efficacy-evaluable 1  patients (n=11), the recommended Phase 2 dose
(LYT-200 12mg/kg in combination with an HMA) demonstrated:

·    27.3% complete response rate

·    9.1% partial response rate

·    9.1% marrow complete response rate

·    45.5% overall response rate

·    18% conversion to transplant rate

 

Due to the number of patients alive at the time of study completion (>50%),
the upper bound of overall survival could not be calculated; therefore, the
median overall survival for this cohort of 6.4 months is not considered fully
mature.

 

Efficacy-evaluable patients had a median of 3 prior lines of therapy (range:
1-5), and all (100%) had previously been treated with an HMA. Additionally,
all patients had high-risk cytogenetics, which - coupled with prior exposure
to treatment - suggests biologically aggressive, treatment-refractory disease
with elevated risk of progression and poor clinical outcomes. Taken together,
these attributes underscore the potential mutation-agnostic mechanism of
LYT-200 and its potential for broad clinical use.

 

R/R AML

Across all efficacy-evaluable(1) patients (n=26), LYT-200 12mg/kg in
combination with VEN/HMA demonstrated:

·    30.8% composite complete response rate 2 ; responders included
patients with mutations associated with VEN resistance

·    7.7% partial response rate

·    42.3% overall response rate

·    19.2% conversion to transplant rate

 

Due to the number of patients alive at the time of study completion (50%), the
upper bound of overall survival could not be calculated; therefore, the median
overall survival for this cohort of 8.2 months is not considered fully
mature.

 

Efficacy-evaluable patients had a median of 2 prior lines of therapy (range:
1-9), and 84.6% had previously been treated with VEN/HMA.

 

INITIAL PHARMACODYNAMIC FINDINGS

The systemic effects of LYT-200 were evaluated through pharmacodynamic
analyses of peripheral blood mononuclear cells, a population of immune cells
in the bloodstream that provides insight into how a treatment affects both the
immune system and leukemic blast cells. These analyses suggest that LYT-200
engages complementary and potentially synergistic pathways directed at cancer
cell killing and anti-cancer immune responses when combined with VEN and
HMA-based therapy, which may contribute to the clinical activity observed in
patients with relapsed/refractory disease following HMA and VEN/HMA treatment,
in MDS and AML, respectively.

 

About Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a group of serious blood cancers
characterized by ineffective blood cell production in the bone marrow, leading
to anemia, infections, and bleeding complications. ( 3 ,  4 ) MDS affects
approximately 60,000-170,000 people in the United States, with an
estimated 30-40% of patients diagnosed with the more aggressive form of the
disease known as high-risk (HR) MDS.(3,  5 ) HR-MDS is associated with poor
outcomes, with median survival typically less than two years
following diagnosis, and approximately 30% of patients progressing to acute
myeloid leukemia (AML).(4)(- 6 )

 

The current standard frontline treatment for HR-MDS are hypomethylating
agents (HMAs), such as azacitidine and decitabine; however, most patients do
not respond to these therapies or eventually stop benefiting from them. 7 
( )Once the disease becomes relapsed or refractory (R/R), outcomes are
especially poor, with survival often limited to only a few months.(7)(, 8 )

 

Treatment options for patients with R/R HR-MDS remain very limited. Only one
therapy has been approved specifically for this setting in the past two
decades, and it targets only a small subset of patients (~3-5%) with a
specific genetic mutation.(7) As a result, there remains a significant need
for new treatment approaches for patients with HR-MDS.

 

About Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive blood cancer characterized by
the rapid growth of abnormal myeloid blast cells in the bone marrow and blood.
It is the most common form of acute leukemia in adults, with a five-year
survival rate of less than 30%. 9  Despite available therapies, many patients
relapse or fail to respond, and outcomes are especially poor in the
relapsed/refractory setting. Around 450,000 people globally are living with
AML.(9)

 

AML is an area of urgent medical need where new therapies with improved
safety, efficacy, and durability or responses are critical. Importantly, the
incidence of AML is increasing, and the market is expected to grow to $6
billion annually by 2030, 10  underscoring the scale of the opportunity to
bring forward therapies that are not only more effective but also applicable
across a broader segment of patients.

 

About LYT-200

LYT-200 is a fully human IgG4 monoclonal antibody in development for the
treatment of hematological malignancies. LYT-200 targets galectin-9, which
is an important oncogenic driver and potent immunosuppressor in cancer,
positioning it as a novel target for cancer therapy. 11  LYT-200 has been
granted Fast Track
(https://news.puretechhealth.com/news-releases/news-release-details/puretech-receives-fda-fast-track-designation-lyt-200-acute)
 and Orphan Drug
(https://news.puretechhealth.com/news-releases/news-release-details/puretech-receives-orphan-drug-designation-lyt-200-acute-myeloid)
 designations from the U.S. Food and Drug Administration (FDA) for the
treatment of acute myeloid leukemia.

 

About Gallop Oncology

Gallop Oncology was founded by and is currently wholly-owned by PureTech
Health plc (Nasdaq: PRTC, LSE: PRTC). Gallop is a clinical-stage
biopharmaceutical company committed to transforming treatment paradigms for
hematologic malignancies. Guided by science and driven to deliver meaningful
outcomes for patients, Gallop is advancing a novel approach where efficacy,
safety, and durability converge. Its lead candidate, LYT-200, is the most
advanced candidate targeting galectin-9, an important oncogenic driver and
potent immunosuppressor in cancer, offering a differentiated strategy to
address some of the most challenging cancers. For more information, please
visit www.galloponcology.com (https://www.galloponcology.com/) .

 

About PureTech Health

PureTech Health is a hub-and-spoke biotherapeutics company dedicated to
giving life to science and transforming innovation into value. We do this
through a proven, capital-efficient R&D model focused on opportunities
with validated pharmacology and untapped potential to address significant
patient needs. This strategy has produced dozens of therapeutic candidates,
including three that have received U.S. FDA approval. By identifying,
shaping, and de-risking these high-conviction assets, and scaling them through
dedicated structures backed by external capital, we accelerate their path to
patients while creating sustainable value for shareholders.

 

For more information, visit www.puretechhealth.com
(http://www.puretechhealth.com/)  or connect with us on X (formerly Twitter)
@puretechh.

 

Cautionary Note Regarding Forward-Looking Statements

This press release contains statements that are or may be forward-looking
statements within the meaning of the Private Securities Litigation Reform Act
of 1995. All statements contained in this press release that do not relate to
matters of historical fact should be considered forward-looking statements,
including without limitation those related to the LYT-200 development program
and development plans, its potential benefits to patients, plans for
discussions with regulatory authorities, the further development of the
program, future presentation of additional data from the program and our
future prospects, developments and strategies. The forward-looking statements
are based on current expectations and are subject to known and unknown risks,
uncertainties and other important factors that could cause actual results,
performance and achievements to differ materially from current expectations,
including, but not limited to, those risks, uncertainties and other important
factors described under the caption "Risk Factors" in our Annual Report on
Form 20-F for the year ended December 31, 2024, filed with the SEC and in
our other regulatory filings. These forward-looking statements are based on
assumptions regarding the present and future business strategies of the
Company and the environment in which it will operate in the future. Each
forward-looking statement speaks only as at the date of this press release.
Except as required by law and regulatory requirements, we disclaim any
obligation to update or revise these forward-looking statements, whether as a
result of new information, future events or otherwise.

 

PureTech

 Public Relations

 publicrelations@puretechhealth.com
(mailto:publicrelations@puretechhealth.com)

 Investor Relations

 IR@puretechhealth.com (mailto:IR@puretechhealth.com)

 UK/EU Media

 Ben Atwell, Rob Winder

+44 (0) 20 3727 1000

 puretech@fticonsulting.com (mailto:puretech@fticonsulting.com)

 US Media

Justin Chen
jchen@tenbridgecommunications.com (mailto:jchen@tenbridgecommunications.com)

 

 

 

 1  Efficacy evaluable is defined in the protocol as all patients who received
a minimum one full cycle of LYT-200 (four doses) and had a minimum of one
post-baseline disease assessment. The intent-to-treat population for the R/R
HR-MDS cohort was n=12 and for the R/R AML cohort was n=33.

 2  Complete response + complete response with incomplete hematological
recovery

 3  American Cancer Society. (2023). What Is Myelodysplastic Syndrome?
Retrieved from https://www.cancer.org (https://www.cancer.org)

 4  National Comprehensive Cancer Network. (2024). NCCN Clinical Practice
Guidelines in Oncology: Myelodysplastic Syndromes (Version 2.2024). Retrieved
from https://www.nccn.org (https://www.nccn.org)

 5  Greenberg, P. L., Tuechler, H., Schanz, J., Sanz, G., Garcia-Manero, G.,
Solé, F., Bennett, J. M., Bowen, D., Fenaux, P., Dreyfus, F., Kantarjian, H.,
Kuendgen, A., Levis, A., Malcovati, L., Cazzola, M., & Haase, D. (2012).
Revised International Prognostic Scoring System for myelodysplastic syndromes.
Blood, 120(12), 2454-2465. https://doi.org/10.1182/blood-2012-03-420489
(https://doi.org/10.1182/blood-2012-03-420489)

 6  Ma, X. (2012). Epidemiology of myelodysplastic syndromes. The American
Journal of Medicine, 125(7 Suppl), S2-S5.
https://doi.org/10.1016/j.amjmed.2012.04.014
(https://doi.org/10.1016/j.amjmed.2012.04.014)

 7  Garcia-Manero, G., Fenaux, P., Al-Kali, A., Baer, M. R., Sekeres, M. A.,
Roboz, G. J., et al. (2016). Rigosertib versus best supportive care for
patients with high-risk myelodysplastic syndromes after failure of
hypomethylating drugs (ONTIME): A randomised, controlled, phase 3 trial.
Lancet Oncology, 17(4), 496-508. https://doi.org/10.1016/S1470-2045(16)00009-7
(https://doi.org/10.1016/S1470-2045(16)00009-7)

 8  Prébet, T., Gore, S. D., Esterni, B., Gardin, C., Itzykson, R., Thepot,
S., Quesnel, B., Dreyfus, F., Beyne-Rauzy, O., Vey, N., Recher, C., Adès, L.,
Fenaux, P., & Groupe Francophone des Myélodysplasies. (2011). Outcome of
patients with higher-risk myelodysplastic syndromes after azacitidine
treatment failure. Journal of Clinical Oncology, 29(24), 3322-3327.
https://doi.org/10.1200/JCO.2011.35.8135
(https://doi.org/10.1200/JCO.2011.35.8135)

 9  Acute Myeloid Leukemia - Cancer Stat Facts. (n.d.). National Cancer
Institute

 10  Grand View Research, Acute Myeloid Leukemia Treatment Market Size, Share
& Trends Analysis Report By Disease, By Treatment (Chemotherapy, Targeted
Therapy, Immunotherapy), By Route of Administration, By End Use, By Region,
And Segment Forecasts, 2025-2030

 11  Karkempetzaki, A. I., Schatton, T., & Barthel, S. R. (2025).
Galectin-9-An emerging Glyco-Immune checkpoint target for cancer therapy.
International Journal of Molecular Sciences, 26(16), 7998.
https://doi.org/10.3390/ijms26167998 (https://doi.org/10.3390/ijms26167998)

 

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