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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d)
of the
Securities Exchange Act of 1934
Date of Report (Date of earliest event
reported): January 10, 2025
MERSANA THERAPEUTICS, INC.
(Exact name of registrant as specified in its
charter)
| Delaware |
|
001-38129 |
|
04-3562403 |
(State or other jurisdiction
of incorporation) |
|
(Commission
File Number) |
|
(IRS Employer
Identification No.) |
840
Memorial Drive
Cambridge,
Massachusetts |
|
02139 |
(Address of Principal Executive Offices)
|
|
(Zip
Code) |
Registrant’s telephone number, including
area code: (617) 498-0020
Not Applicable
(Former name or former address, if changed since
last report)
Check the appropriate box below if the Form 8-K filing is intended
to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):
¨ Written
communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨ Soliciting
material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
¨ Pre-commencement
communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
¨ Pre-commencement
communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
Securities registered pursuant to Section 12(b)
of the Act:
| Title
of each class |
Trading
Symbol(s) |
Name
of each exchange on which registered |
| Common Stock, $0.0001 par value |
MRSN |
The Nasdaq Stock Market LLC |
Indicate by check mark whether the registrant is an emerging growth
company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange
Act of 1934 (§240.12b-2 of this chapter).
Emerging growth company ¨
If an emerging
growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any
new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨
| Item 7.01 | Regulation FD Disclosure. |
On January 10, 2025,
Mersana Therapeutics, Inc. (the “Company”) issued two press releases, titled “Mersana Therapeutics Announces Positive
Initial Clinical Data from Phase 1 Clinical Trial of Emiltatug Ledadotin (XMT-1660); Initiation of Expansion in Triple Negative Breast
Cancer” and “Mersana Therapeutics Announces Additional FDA Fast Track Designation Granted to Emiltatug Ledadotin (XMT-1660).”
Copies of these press releases are being furnished as Exhibits 99.1 and 99.2, respectively, to this Current Report on Form 8-K (the “Report”).
The information furnished in this Item 7.01, including Exhibits 99.1
and 99.2, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended
(the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall such information be deemed to be
incorporated by reference in any filing by the Company with the Securities and Exchange Commission (“SEC”) under the Securities
Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language contained
in such a filing, except as expressly set forth by specific reference in such a filing.
Fast Track Designation
On January 10, 2024, the Company announced
that the World Health Organization has approved emiltatug ledadotin as the international nonproprietary name for XMT-1660, the Company’s
lead Dolasynthen antibody-drug conjugate (“ADC”) candidate targeting B7-H4. The Company refers to emiltatug ledadotin as “Emi-Le.”
The Company also announced that the U.S. Food and Drug Administration (“FDA”) recently granted an additional Fast Track designation
to Emi-Le. The new Fast Track designation is for the treatment of advanced or metastatic breast cancer in patients with human epidermal
growth factor receptor 2- (“HER2-”) low (IHC 1+ or IHC 2+/ISH–) or HER2-negative (IHC 0) disease, including triple-negative
breast cancer (“TNBC”), who have received a prior topoisomerase-1 inhibitor (“topo-1”) ADC. Additionally, hormone-receptor
positive (“HR+”) patients should also have received or be ineligible for endocrine therapy. The FDA previously granted Fast
Track designation to Emi-Le for the treatment of adult patients with advanced or metastatic recurrent TNBC.
Initial
Phase 1 Dose Escalation Data for Emi-Le; Initiation of Dose Expansion
On January
10, 2024, the Company also announced positive initial clinical data from the dose escalation and backfill cohorts of its Phase 1 clinical
trial of Emi-Le and announced the initiation of the dose expansion portion of the clinical trial.
As of
the December 13, 2024 data cut date, the dose escalation portion of the Company’s Phase 1 clinical trial of Emi-Le had enrolled
a total of 130 patients with advanced/metastatic TNBC; HR+/HER2-negative breast cancer; ovarian cancer; endometrial cancer and adenoid
cystic carcinoma type 1. The enrolled patient population was heavily pretreated, with patients receiving up to 15 and a median of 4.5
prior lines of therapy, and approximately 92% of enrolled patients with TNBC had been previously treated with at least one topo-1 ADC.
The Company retrospectively analyzed tumor samples from patients in the trial. As of the data cut date, the Company had determined B7-H4
tumor expression for 103 patients. Among the 103 patients with known B7-H4 tumor expression, approximately 44% had a tumor proportion
score of 70% or higher, which the Company has preliminarily characterized as “B7-H4 High.”
Emi-Le
was observed to be generally well tolerated, with no Grade 4 or 5 treatment-related adverse events (“TRAEs”) reported as of
the data cut date. The most common TRAEs of any grade across the entire patient population were transient aspartate aminotransferase (“AST”)
increase (38% of patients), generally asymptomatic and reversible proteinuria (31%), generally low-grade nausea (29%) and low-grade fatigue
(28%). The only Grade 3 TRAEs in ≥5% or more of all patients were AST increase (14%) and proteinuria (9%). Across the entire enrolled
patient population, TRAEs leading to discontinuation, dose reduction and dose delay were observed in 2.3%, 9.2% and 12.3% of patients,
respectively. No dose-limiting treatment-related neutropenia, neuropathy, ocular toxicity, interstitial lung disease or thrombocytopenia
were reported, which the Company believes differentiates Emi-Le from many other approved and clinical-stage ADCs.
The dose escalation portion of the clinical
trial evaluated doses ranging from 7.2 milligrams per meter squared (mg/m2) to 115 mg/m2 as well as the following
dosing schedules: once every four weeks (“Q4W”), once every three weeks (“Q3W”) and on days 1 and 8 of a 28-day
cycle (“D1+8 Q4W”). The trial protocol allows for the enrollment of patients in backfill cohorts at selected dose levels.
The Company has analyzed initial trial data as of the data cut date across the entire trial population and in three dose groups: those
in a “Subtherapeutic Dose Range” from 7.2 to 28.7 mg/m2 per cycle, an “Intermediate Dose Range” from
38.1 to 67.4 mg/m2 per cycle and a “High Dose Range” at or above 76.2 mg/m2 per cycle.
In the Intermediate Dose Range,
the confirmed objective response rate (“ORR”) among evaluable patients (those with measurable disease at baseline and at least
one post-baseline scan) was 23% (6 of 26 patients) across all B7-H4 High tumors and 23% (3 of 13 patients) with B7-H4 High TNBC, all of
whom had previously been treated with at least one topo-1 ADC.
In the
ASCENT Phase 3 clinical trial of sacituzumab govitecan, a topo-1 ADC, the ORR with standard-of-care single-agent chemotherapy in relapsed/refractory
TNBC was approximately 5% with progression free survival of approximately seven weeks. Based on these encouraging Emi-Le data in the Intermediate
Dose Range, the Company has advanced a dose of 67.4 mg/m2 Q4W into a dose expansion cohort in patients with TNBC who have received
one to four prior treatment lines, including at least one prior topo-1 ADC (“post-topo-1 TNBC”).
In the
High Dose Range, the confirmed ORR among evaluable patients was 22% (2 of 9 patients) across all B7-H4 High tumors. Additionally, 78%
(7 of 9 patients) had ≥30% tumor reduction in target lesions. In the High Dose Range, objective responses in multiple evaluable patients
with B7-H4 High tumors were not confirmed after protocol-mandated dose delays for proteinuria. The Company is implementing proteinuria
mitigation efforts and continues to explore the High Dose Range in dose escalation and backfill cohorts to identify a second dose for
investigation in post-topo-1 TNBC in the expansion portion of the trial.
Furthermore,
on January 10, 2024, the Company will host a webinar to discuss its initial clinical data with investors. A copy of the slide presentation
for the Company’s webinar is being filed as Exhibit 99.3 to this Report and is incorporated by reference herein. The Company undertakes
no obligation to update, supplement or amend the materials attached hereto as Exhibit 99.3.
2025 Anticipated Milestones and Anticipated
Cash Runway
On January 10, 2024, the Company also announced its expected 2025 milestones,
which are as follows:
Emi-Le
| · | First Half 2025: Continue enrollment in expansion at a dose of 67.4 mg/m2
Q4W in post-topo-1 TNBC |
| · | 2025: Initiate enrollment in expansion at a second dose in post-topo-1 TNBC |
| · | 2025: Present additional Phase 1 clinical data from dose escalation and backfill
cohorts |
XMT-2056, the Company’s lead Immunosynthen ADC targeting a
novel HER2 epitope
| · | 2025: Present initial clinical pharmacodynamic STING activation data |
Pipeline
| · | Continue to support internal pipeline and existing collaborations with Johnson
& Johnson and Merck KGaA, Darmstadt, Germany |
As previously reported, the Company’s
cash, cash equivalents and marketable securities as of September 30, 2024 were $155.2 million. As of January 10, 2025, the company
continues to expect that its capital resources will be sufficient to support its current operating plan commitments into 2026.
Forward-Looking Statements
This Report contains “forward-looking” statements and information
within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified by words such as “aims,”
“anticipates,” “believes,” “could,” “estimates,” “expects,” “forecasts,”
“goal,” “intends,” “may,” “plans,” “possible,” “potential,” “seeks,”
“will” and variations of these words or similar expressions, although not all forward-looking statements contain these words.
Forward-looking statements in this Report include, but are not limited to, statements concerning the Company’s plans regarding the
clinical development of Emi-Le and XMT-2056, including with respect to the progress and design of the clinical trials of these product
candidates; the potential clinical benefits of Emi-Le; the Company’s efforts to identify an additional dose for investigation in
the expansion portion of its Phase 1 clinical trial of Emi-Le; the Company’s planned data presentations, including with respect
to its Phase 1 clinical trial of Emi-Le and to clinical pharmacodynamic STING activation data related to XMT-2056; the Company’s
collaborations with third parties; the development and potential of the Company’s product candidates, platforms, technology and
pipeline of ADC candidates; and the Company’s expected cash runway. The Company may not actually achieve the plans, intentions or
expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements.
Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements
as a result of various factors, including, among other things, uncertainties inherent in research and development, in the advancement,
progression and completion of clinical trials and in the clinical development of the Company’s product candidates, including Emi-Le
and XMT-2056; the risk that the Company may face delays in patient enrollment in its Phase 1 clinical trials of Emi-Le and XMT-2056; the
risk that outcomes of preclinical studies may not be predictive of clinical trial results; the risk that initial or interim results from
a clinical trial may not be predictive of the final results of the trial or the results of future trials; the risk that clinical trial
data may not support regulatory applications or approvals; the risk that the Company may not realize the intended benefits of its platforms,
technology and collaborations; the risk that the Company’s the Company regarding its expected cash runway are inaccurate or that
the conduct of its business requires more cash than anticipated; and other important factors, any of which could cause the Company’s
actual results to differ from those contained in the forward-looking statements, that are described in greater detail in the section entitled
“Risk Factors” in the Company’s Quarterly Report on Form 10-Q
filed with the SEC on November 13, 2024, as well as in other filings the Company may make with the SEC in the future. Any forward-looking
statements contained in this Report speak only as of the date hereof, and the Company expressly disclaims any obligation to update any
forward-looking statements contained herein, whether because of any new information, future events, changed circumstances or otherwise,
except as otherwise required by law.
| Item 9.01. | Financial Statements and Exhibits. |
(d) Exhibits
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
| |
MERSANA THERAPEUTICS, INC. |
| |
|
|
| Date: January 10, 2025 |
By: |
/s/
Brian DeSchuytner |
| |
|
Brian DeSchuytner |
| |
|
Senior Vice President, Chief Operating Officer and
Chief Financial Officer |
Exhibit 99.1
Mersana Therapeutics Announces Positive Initial
Clinical Data from Phase 1 Clinical Trial of Emiltatug Ledadotin (XMT-1660); Initiation of Expansion in Triple Negative Breast Cancer
| - | Emiltatug ledadotin observed to be generally well tolerated with differentiated safety and tolerability profile |
| - | Promising clinical activity observed in patients with triple-negative breast cancer (TNBC) previously treated with topoisomerase-1
inhibitor (topo-1) ADCs; confirmed responses observed across all enrolled tumor types |
| - | First expansion cohort initiated in patients with TNBC previously treated with at least one topo-1 ADC; dose exploration efforts
ongoing |
| - | Company announces expected 2025 milestones and areas of focus |
| - | Conference call today at 8:30 a.m. ET |
CAMBRIDGE, Mass., January 10, 2025 – Mersana Therapeutics,
Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates
(ADCs) targeting cancers in areas of high unmet medical need, today announced positive initial clinical data from the Phase 1 dose escalation
and backfill cohorts for emiltatug ledadotin (Emi-Le; XMT-1660), Mersana’s lead Dolasynthen ADC candidate targeting B7-H4.
“We
believe the initial safety, tolerability and efficacy data for Emi-Le demonstrate a profile that is exciting and differentiated within
both the B7-H4 field and the broader ADC landscape,” said Martin Huber, M.D., President and Chief Executive Officer of Mersana
Therapeutics. “We have observed clinical activity across tumors, including in heavily pre-treated patients with TNBC. These clinical
data have led us to initiate expansion in patients with TNBC who have previously been treated with at least one topo-1 ADC, a population
with very high unmet need.”
As of a December 13, 2024 data cutoff, the dose escalation portion
of the Emi-Le Phase 1 clinical trial enrolled a total of 130 patients with advanced/metastatic TNBC; hormone-receptor-positive, human
epidermal growth factor receptor 2 negative breast cancer; ovarian cancer; endometrial cancer and adenoid cystic carcinoma type 1. The
enrolled patient population was heavily pretreated, with patients receiving up to 15 and a median of 4.5 prior lines of therapy, and approximately
92% of enrolled patients with TNBC had been previously treated with at least one topo-1 ADC. Among the 103 patients with known B7-H4 tumor
expression, approximately 44% had a tumor proportion score of 70% or higher, which Mersana has preliminarily characterized as “B7-H4
high.”
Emi-Le was observed to be generally well tolerated, with no Grade 4
or 5 treatment-related adverse events (TRAEs) reported. The most common TRAEs of any grade across the entire patient population were transient
aspartate aminotransferase (AST) increase (38% of patients), generally asymptomatic and reversible proteinuria (31%), generally low-grade
nausea (29%) and low-grade fatigue (28%). The only Grade 3 TRAEs in ≥5% or more of all patients were AST increase (14%) and proteinuria
(9%). Across the entire enrolled patient population, TRAEs leading to discontinuation, dose reduction and dose delay were observed in
2.3%, 9.2% and 12.3% of patients, respectively. No dose-limiting treatment-related neutropenia, neuropathy, ocular toxicity, interstitial
lung disease or thrombocytopenia were reported, which the company believes differentiates Emi-Le from many other approved and clinical-stage
ADCs.
At intermediate doses in the trial (38.1 mg/m2 to 67.4 mg/m2),
the confirmed objective response rate (ORR) among evaluable patients (those with measurable disease at baseline and at least one post-baseline
scan) was 23% (6 of 26 patients) across all B7-H4 high tumors and 23% (3 of 13 patients) with B7-H4 high TNBC, all of whom had previously
been treated with at least one topo-1 ADC.
In the ASCENT Phase 3 clinical trial of sacituzumab govitecan, a topo-1
ADC, the ORR with standard-of-care single-agent chemotherapy in relapsed/refractory TNBC was approximately 5% with progression free survival
of approximately seven weeks. Based on these encouraging Emi-Le data at intermediate doses, Mersana has advanced a dose of 67.4 mg/m2
every four weeks (Q4W) into an expansion cohort in patients with TNBC who have received one to four prior treatment lines, including at
least one prior topo-1 ADC.
“In terms of both tolerability and clinical activity, these Emi-Le
data are encouraging,” Erika Hamilton, M.D., Director Breast Cancer Research, Sarah Cannon Research Institute in Nashville, Tennessee,
said, “It is notable that all the TNBC patients who responded to Emi-Le had previously been treated with at least one topo-1 ADC.
The results indicate that Emi-Le may help address an already substantial and growing need among topo-1 experienced breast cancer patients
for new treatments.”
At high doses above 76 mg/m2, the confirmed ORR among evaluable
patients was 22% (2 of 9 patients) across all B7-H4 high tumors. Additionally, 78% (7 of 9 patients) had ≥30% tumor reduction in target
lesions. At these high dose levels, objective responses in multiple evaluable patients with B7-H4 high tumors were not confirmed after
protocol-mandated dose delays for proteinuria. Mersana is implementing proteinuria mitigation efforts and continues to explore higher
doses in dose escalation and backfill cohorts to identify a second dose for the expansion portion of the trial.
Mersana’s Expected 2025 Milestones and Areas of Focus
Emi-Le
| · | 1H2025: Continue enrollment in expansion at a dose of 67.4 mg/m2
Q4W in patients with TNBC who have previously received at least one prior topo-1 ADC |
| · | 2025: Initiate enrollment in expansion at a second dose in patients with
TNBC who have previously received at least one prior topo-1 ADC |
| · | 2025: Present additional Phase 1 clinical data from dose
escalation and backfill cohorts |
XMT-2056, Mersana’s lead Immunosynthen ADC targeting a novel
HER2 epitope
| · | 2025: Present initial clinical pharmacodynamic STING activation data |
Pipeline
| · | Continue to support internal pipeline and existing collaborations with Johnson
& Johnson and Merck KGaA, Darmstadt, Germany |
Conference Call Information
Mersana will host a conference call
today at 8:30 a.m. ET to discuss the initial clinical data from its Phase 1 clinical trial of Emi-Le. To access the call, please dial
833-255-2826 (domestic) or 412-317-0689 (international). A live webcast that includes the data presentation will be available on
the Investors & Media section of the Mersana website at www.mersana.com, and a replay of the webcast will be available in the
same location following the conference call for approximately 90 days.
About Mersana Therapeutics
Mersana Therapeutics
is a clinical-stage biopharmaceutical company focused on the development of novel antibody-drug conjugates (ADCs) and driven by the knowledge
that patients are waiting for new treatment options. The company has developed proprietary cytotoxic (Dolasynthen) and immunostimulatory
(Immunosynthen) ADC platforms that are generating a pipeline of wholly-owned and partnered product candidates with the potential to treat
a range of cancers. Its pipeline includes Emi-Le (emiltatug ledadotin; XMT-1660), a Dolasynthen ADC targeting B7-H4, and XMT-2056, an
Immunosynthen ADC targeting a novel epitope of human epidermal growth factor receptor 2 (HER2). Mersana routinely posts information that
may be useful to investors on the “Investors & Media” section of its website at www.mersana.com.
Forward-Looking Statements
This press release contains “forward-looking” statements
and information within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified by words
such as “aims,” “anticipates,” “believes,” “could,” “estimates,” “expects,”
“forecasts,” “goal,” “intends,” “may,” “plans,” “possible,” “potential,”
“seeks,” “will” and variations of these words or similar expressions, although not all forward-looking statements
contain these words. Forward-looking statements in this press release include, but are not limited to, statements concerning Mersana’s
plans regarding the clinical development of Emi-Le and XMT-2056, including with respect to the progress and design of the clinical trials
of these product candidates; the potential clinical benefits of Emi-Le; Mersana’s efforts to identify an additional dose for investigation
in the expansion portion of its Phase 1 clinical trial of Emi-Le; Mersana’s planned data presentations, including with respect to
its Phase 1 clinical trial of Emi-Le and to clinical pharmacodynamic STING activation data related to XMT-2056; Mersana’s collaborations
with third parties; and the development and potential of Mersana’s product candidates, platforms, technology and pipeline of ADC
candidates. Mersana may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and
you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans,
intentions and expectations disclosed in these forward-looking statements as a result of various factors, including, among other things,
uncertainties inherent in research and development, in the advancement, progression and completion of clinical trials and in the clinical
development of Mersana’s product candidates, including Emi-Le and XMT-2056; the risk that Mersana may face delays in patient enrollment
in its Phase 1 clinical trials of Emi-Le and XMT-2056; the risk that outcomes of preclinical studies may not be predictive of clinical
trial results; the risk that initial or interim results from a clinical trial may not be predictive of the final results of the trial
or the results of future trials; the risk that clinical trial data may not support regulatory applications or approvals; the risk that
Mersana may not realize the intended benefits of its platforms, technology and collaborations; and other important factors, any of which
could cause Mersana’s actual results to differ from those contained in the forward-looking statements, that are described in greater
detail in the section entitled “Risk Factors” in Mersana’s Quarterly Report on Form 10-Q filed with the Securities and
Exchange Commission (“SEC”) on November 13, 2024, as well as in other filings Mersana may make with the SEC in the future.
Any forward-looking statements contained in this press release speak only as of the date hereof, and Mersana expressly disclaims any obligation
to update any forward-looking statements contained herein, whether because of any new information, future events, changed circumstances
or otherwise, except as otherwise required by law.
###
Contact:
Jason Fredette
617-498-0020
jason.fredette@mersana.com
Exhibit 99.2
Mersana Therapeutics Announces Additional FDA
Fast Track Designation Granted
to Emiltatug Ledadotin (XMT-1660)
Conference call to discuss positive initial
Phase 1 clinical data today at 8:30 a.m. ET
CAMBRIDGE, Mass., January 10, 2025 – Mersana Therapeutics,
Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates
(ADCs) targeting cancers in areas of high unmet medical need, today announced the U.S. Food and Drug Administration (FDA) recently granted
an additional Fast Track designation to XMT-1660. The company also announced that the World Health Organization has approved emiltatug
ledadotin (abbreviated as Emi-Le) as XMT-1660’s international nonproprietary name (INN).
The new Fast Track designation is for the treatment of advanced or
metastatic breast cancer in patients with human epidermal growth factor receptor 2 (HER2) low (IHC 1+ or IHC 2+/ISH–) or HER2-negative
(IHC 0) disease, including triple-negative breast cancer (TNBC), who have received a prior topoisomerase-1 inhibitor ADC. Additionally,
hormone-receptor positive patients should also have received or be ineligible for endocrine therapy. The FDA previously granted Fast Track
designation to Emi-Le for the treatment of adult patients with advanced or metastatic recurrent TNBC.
“Topoisomerase-1 inhibitor ADCs are
rapidly becoming the standard of care for metastatic TNBC and hormone-receptor positive breast cancer, and an increasing amount of
research shows that these patients are exceedingly difficult to treat thereafter,” said Martin Huber, M.D., President and
Chief Executive Officer of Mersana Therapeutics. “This growing population is a primary focus for us as we advance the
development of Emi-Le. We are excited to announce this additional Fast Track designation and the initial clinical data from our
ongoing Phase 1 clinical trial that were press released separately this morning.”
The FDA’s Fast Track program is designed to facilitate the development
and expedite the review of drug candidates to treat serious conditions and fill an unmet medical need. A product candidate granted Fast
Track designation may be eligible for several benefits, including more frequent meetings and communications with the FDA and, if certain
criteria are met, the potential for Accelerated Approval, Priority Review or Rolling Review of a Biologics License Application (BLA) by
the FDA.
Conference Call Information
Mersana will host
a conference call today at 8:30 a.m. ET to discuss the initial clinical data from its Phase 1 clinical trial of Emi-Le. To access the
call, please dial 833-255-2826 (domestic) or 412-317-0689 (international). A live webcast that includes the data presentation
will be available on the Investors & Media section of the Mersana website at www.mersana.com, and a replay of the webcast
will be available in the same location following the conference call for approximately 90 days.
About Mersana Therapeutics
Mersana Therapeutics
is a clinical-stage biopharmaceutical company focused on the development of novel antibody-drug conjugates (ADCs) and driven by the knowledge
that patients are waiting for new treatment options. The company has developed proprietary cytotoxic (Dolasynthen) and immunostimulatory
(Immunosynthen) ADC platforms that are generating a pipeline of wholly-owned and partnered product candidates with the potential to treat
a range of cancers. Its pipeline includes Emi-Le (emiltatug ledadotin; XMT-1660), a Dolasynthen ADC targeting B7-H4, and XMT-2056, an
Immunosynthen ADC targeting a novel epitope of human epidermal growth factor receptor 2 (HER2). Mersana routinely posts information that
may be useful to investors on the “Investors & Media” section of its website at www.mersana.com.
Forward-Looking Statements
This press release
contains “forward-looking” statements and information within the meaning of the Private Securities Litigation Reform Act of
1995. These statements may be identified by words such as “aims,” “anticipates,” “believes,” “could,”
“estimates,” “expects,” “forecasts,” “goal,” “intends,” “may,”
“plans,” “possible,” “potential,” “seeks,” “will” and variations of these
words or similar expressions, although not all forward-looking statements contain these words. Forward-looking statements in this press
release include, but are not limited to, those concerning Mersana’s areas of focus; the continued development and therapeutic potential
of Mersana’s product candidates, including Emi-Le (XMT-1660); Mersana’s anticipated disclosure of initial clinical trial data
from its Phase 1 clinical trial of Emi-Le; and the potential advantages of Fast Track Designation. Mersana may not actually achieve the
plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking
statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking
statements as a result of various factors, including, among other things, uncertainties inherent in research and development and clinical
development of Mersana’s product candidates, including Emi-Le; whether the outcomes of preclinical studies will be predictive of
clinical trial results; the risk that the receipt of Fast Track designation for Emi-Le may not result in a faster development or regulatory
review or approval process compared to products considered for approval under conventional FDA procedures the risk that the FDA may later
decide that Emi-Le no longer meets the conditions for Fast Track designation or decide that the time period for FDA review or approval
will not be shortened; the risk that Mersana may not realize the intended benefits of its platforms, technology and collaborations;
and other important factors, any of which could cause Mersana’s actual results to differ from those contained in the forward-looking
statements, that are described in greater detail in the section entitled “Risk Factors” in Mersana’s Quarterly Report
on Form 10-Q filed with the Securities and Exchange Commission (“SEC”) on November 13, 2024, as well as in other filings Mersana
may make with the SEC in the future. Any forward-looking statements contained in this press release speak only as of the date hereof,
and Mersana expressly disclaims any obligation to update any forward-looking statements contained herein, whether because of any new information,
future events, changed circumstances or otherwise, except as otherwise required by law.
Contact:
Jason Fredette
617-498-0020
jason.fredette@mersana.com
Exhibit 99.3
Initial Phase 1 Dose Escalation Data for Emi - Le ( emiltatug ledadotin ; XMT - 1660) January 10, 2025
Legal Disclaimer 2 This presentation contains “forward - looking” statements and information within the meaning of the Private Securities Litigation Reform Act of 1995 . These statements may be identified by words such as “aims,” “anticipates,” “believes,” “could,” “estimates,” “expects,” “forecasts,” “goal,” “intends,” “may,” “plans,” “possible,” “potential,” “seeks,” “will” and variations of these words or similar expressions, although not all forward - looking statements contain these words . Forward - looking statements in this presentation include, but are not limited to, statements regarding Mersana Therapeutics, Inc . ’s (“Mersana”) business strategy, mission and vision ; the development and potential of Mersana’s product candidates and platforms, including Emi - Le (XMT - 1660 ) and Dolasynthen ; the potential clinical benefits of Emi - Le ; and the design, progression and timing of Mersana’s clinical trial of Emi - Le . Mersana may not actually achieve the plans, intentions or expectations disclosed in these forward - looking statements, and you should not place undue reliance on these forward - looking statements . Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward - looking statements as a result of various factors, including, among other things, uncertainties inherent in research and development, in the advancement, progression and completion of clinical trials and in the clinical development of Mersana's product candidates, including Emi - Le and XMT - 2056 ; the risk that Mersana may not realize the intended benefits of its platforms, technology and collaborations ; the risk that outcomes of preclinical studies may not be predictive of clinical trial results ; the risk that initial or interim results from a clinical trial may not be predictive of the final results of the trial or the results of future trials ; the risk that clinical trial data may not support regulatory applications or approvals ; the risk that Mersana may not realize the intended benefits of its platforms, technology and collaborations ; and other important factors, any of which could cause Mersana's actual results to differ from those contained in the forward - looking statements, that are described in greater detail in the section entitled “Risk Factors” in Mersana’s Quarterly Report on Form 10 - Q filed with the Securities and Exchange Commission (“SEC”) on November 13 , 2024 , as well as in other filings Mersana may make with the SEC in the future . New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties . Any forward - looking statements contained in this presentation speak only as of the date of this presentation, and Mersana expressly disclaims any obligation to update any forward - looking statements contained herein, whether because of any new information, future events, changed circumstances or otherwise, except as otherwise required by law . Mersana owns various trademark registrations and applications, and unregistered trademarks, including Mersana’s name and its corporate logo . All other trade names, trademarks and service marks of other companies appearing in this presentation are the property of their respective holders . Solely for convenience, the trademarks and trade names in this presentation may be referred to without the ®, or © symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto . Mersana does not intend to use or display other companies' trademarks and trade names to imply a relationship with, or endorsement or sponsorship of Mersana by, any other companies .
3 While today’s ADCs provide substantial benefits to some patients, significant platform and payload limitations remain. Mersana is focused on developing novel platforms and payloads that enable ADCs with meaningfully improved safety and efficacy. ADCs, antibody - drug conjugates
Lack of Platform and Payload Innovation Cytotoxic ADCs remain predominant with few novel mechanisms Innovating to Overcome Today's ADC Limitations 4 ADC, antibody - drug conjugate; ILD, interstitial lung disease; IO, immuno - oncology; STING, STimulator of INterferon Genes; topo - 1, topoisomerase - 1 inhibitor ADCs TODAY First - Generation ADCs Limited by Safety First wave of anti - tubulins dose limited by platform toxicities (neuropathy, neutropenia, ocular toxicity, etc.) Establish the Best - In - Class Anti - Tubulin Platform Dolasynthen designed to overcome dose - limiting ADC platform toxicities to drive greater efficacy and enable combinations with standards of care THE MERSANA OPPORTUNITY Newer Topo ADC Barriers Emerging Hematologic toxicities, ILD and topo - after - topo resistance are limiting this class Provide Effective Alternatives to Topo - 1 ADCs Allow for ADCs that avoid resistance mechanisms, severe hematologic toxicities and ILD Establish a New Class of IO ADCs Advance ADCs beyond cytotoxics using STING - agonism to achieve tumor - specific activation of the innate immune system Focus for Today
Background on B7 - H4 and Emi - Le B7 - H4 Target: Clinically validated and highly expressed in a range of solid tumors with limited healthy tissue expression • Novel ADC Design: Homogeneous DAR 6 Dolasynthen ADC (site - specific bioconjugation; proprietary auristatin payload) • Two FDA Fast Track Designations Granted: – Advanced or metastatic recurrent TNBC – Advanced or metastatic HER - 2 low / HER - 2 negative breast cancer post - topo - 1 ADC (including TNBC and certain HR+ breast cancers 2 ) • High Unmet Need in TNBC: – ASCENT Phase 3 clinical trial of sacituzumab govitecan showed PFS of ~7 weeks and ORR of ~5% for standard of care single - agent chemo in relapsed/refractory TNBC 3 – Global relapsed/refractory TNBC market projected to exceed $1 billion annually starting in 2025 4 5 Emi - Le 1. Sachdev et al. ASCO 2019 2. Patients who have received or are ineligible for endocrine therapy 3. Bardia et al. NEJM 2021 April 22; 384(16): 1529 - 1541 4. Based on TD Cowen analyst estimate in November 2024 report for global sales of approved therapeutic for treatment of relapsed /re fractory TNBC ADC, antibody - drug conjugate; DAR, drug - to - antibody ratio; FDA, U.S. Food and Drug Administration; HNSCC, head and neck squamous cell carcinoma; HER - 2, human e pidermal growth f actor r eceptor 2; HR+, hormone - receptor positive; IHC, immunohistochemistry; ORR, objective response rate per RECIST version 1.1; TNBC, triple - negative breast cancer; PFS, progression - free survival; sqNSCLC , squamous non - small - cell lung cancer
• Most common TRAEs: transient AST increase; low - grade nausea and fatigue; generally asymptomatic and reversible proteinuria • No Grade 4 or Grade 5 TRAEs reported; no dose - limiting treatment - related neutropenia, neuropathy, ocular toxicity, ILD or thrombocytopenia reported • Profile may enable combinations with platinum chemotherapy, other ADCs, PD - (L)1, etc. • 7 of 9 evaluable patients with B7 - H4 high tumors had ≥30% tumor reductions in target lesions; 2 confirmed responses • Implementing proteinuria mitigation efforts and continuing dose exploration in High Dose Range to identify a second expansion dose • Encouraging clinical activity and tolerability in Intermediate Dose Range (38.1 – 67.4 mg/m 2 ): – 23% confirmed ORR (6/26) in evaluable patients with B7 - H4 high tumors – 23% confirmed ORR (3/13) in evaluable patients with B7 - H4 high TNBC post - topo - 1 ADCs • Expansion underway at high end of Intermediate Dose Range (67.4 mg/m 2 Q4W) in TNBC post - topo - 1 ADC; high unmet need (~5% ORR and ~7 week PFS for standard of care 1 ) Emi - Le: A Potential Best - in - Class B7 - H4 ADC 6 Potential for Even Greater Clinical Activity in High Dose Range Encouraging Clinical Activity Observed in Post - Topo - 1 TNBC; Expansion Initiated Differentiated Safety and Tolerability Profile 1. Bardia et al. NEJM 2021 April 22; 384(16): 1529 - 1541 ADC, antibody - drug conjugate; mg/m 2 , milligrams per meter squared; ORR, objective response rate per RECIST version 1.1; PD - (L)1, programmed cell death ligand 1; PF S, progression - free survival; PRs, partial responses; Q4W, dosing every four weeks; TNBC, triple - negative breast cancer; topo - 1, topoisomerase - 1 inhibitor; TRAEs, treatment - related adverse event s; ILD, interstitial lung disease December 13, 2024 data cutoff
Trial Design and Demographics
Emi - Le Phase 1 Dose Escalation Design 8 • In parallel with DES, backfill cohorts are enrolling additional participants at multiple dose levels • Each backfill cohort is enrolling up to 12 patients and may focus on tumor types of particular interest • Data from both DES and backfill cohorts will be utilized to determine the RP2D Indications Being Enrolled Include: Triple - Negative Breast Cancer HR+ Breast Cancer Endometrial Cancer Ovarian Cancer Adenoid Cystic Carcinoma – Type 1 Dose Escalation (DES) Primary Endpoints MTD , s afety and tolerability Secondary Endpoints ORR, DOR , DCR, PK, ADA Backfill Cohorts Primary Endpoint Safety and tolerability Secondary Endpoints ORR, DOR, DCR, PK, ADA ADA, anti - drug antibody; DCR, disease control rate; DOR, duration of response; HR+, hormone - receptor - positive, human e pidermal growth f actor r eceptor 2 negative breast cancer ; MTD, maximum tolerated dose; ORR, objective response rate per RECIST version 1.1; PK, pharmacokinetics; RP2D, recommended Phase 2 dose B7 - H4 expression being assessed retrospectively based on fresh or archived tissue to inform biomarker strategy; investigating dose levels and schedules in parallel escalation and backfill cohorts to optimize profile for expansion
Broad range of doses and multiple dosing schedules investigated Phase 1 Dose Escalation and Backfill Enrollment 9 Doses and Schedules Investigated (in mg/m 2 per cycle) 67.4 (n=4) 80.0 (n=11) 95.0 (n=5) 38.1x2 (n=9) 44.5x2 (n=10) 1 38.1 (n=12) 44.5 (n=8) 50.7 (n=14) 59.0 (n=14) 67.4 (n=15) 28.7x2 (n=3) 7.2 (n=1) 14.4 (n=3) 21.6 (n=3) 28.7 (n=6) 28.7 (n=3) 115.0 (n=3) Subtherapeutic Dose Range Q3W Q4W D1+8 Q4W Intermediate Dose Range High Dose Range 38.1 (n=6) 1. Includes four patients who were enrolled to receive this starting dose and a pre - specified modified dose following cycle 1 Q3W, dosing once every three weeks; Q4W, dosing once every four weeks; AST, aspartate aminotransferase; D1+8 Q4W, dosing on d ays one and eight every four weeks; DLT, dose - limiting toxicity; mg/kg, milligrams per kilogram; mg/m 2 , milligrams per meter squared; TNBC, triple - negative breast cancer; topo - 1, topoisomerase - 1 inhibitor Initial dose selected for expansion ~1 mg/kg per cycle ~2 mg/kg per cycle • 130 patients dosed as of December 13, 2024 data cutoff • 5 DLTs observed: – Three Grade 3 transient AST increases (one at 59 mg/m 2 Q4W and two at 115 mg/m 2 Q4W); 115 mg/m 2 deemed to be a non - tolerated dose – One reversible Grade 3 proteinuria accompanied by peripheral oedema at 80 mg/m 2 Q4W (event confounded by concurrent gout flare) – One Grade 3 pyrexia at 44.5 mg/m 2 D1+8 Q4W (self - reported and rapidly resolved) • Expansion initiated at 67.4 mg/m 2 Q4W in TNBC post - topo - 1 ADC; continuing dose exploration in High Dose Range
Majority of patients had breast cancer and received ≥1 prior topo - 1 ADC Dose Escalation and Backfill Demographics 10 1. 11 of 63 (17%) of TNBC patients had a primary diagnosis of HR+ breast cancer 2. For this preliminary analysis, TPS ≥70 determined to be “TPS high”. Final B7 - H4 TPS cutoff for Emi - Le monotherapy development to be determined in dose expansion. ACC - 1, a denoid cystic c arcinoma – type 1; ADC, antibody - drug conjugate; HR+/HER2 - BC, hormone - receptor - positive, human e pidermal growth f actor r eceptor 2 negative breast cancer; TNBC, triple - negative breast cancer; topo - 1, topoisomerase - 1 inhibitor; TPS, tumor proportion score Total (N=130) ACC - I (N=7) Endometrial (N=12) Ovarian (N=14) HR+/HER2 - BC (N=34) TNBC 1 (N=63) 55 55 65 61 62 48 Median age 4.5 (0 - 15) 0 (0 - 3) 2.5 (1 - 4) 5 (2 - 11) 7 (2 - 15) 4 (2 - 9) Median prior lines (range) Prior topo - 1 ADCs received, n (%) 36 (27.7%) 0 0 0 15 (44.1%) 21 (33.3%) Prior trastuzumab deruxtecan 69 (53.1%) 0 0 0 15 (44.1%) 54 (85.7%) Prior sacituzumab govitecan 27 (20.8%) 0 0 0 10 (29.4%) 17 (27.0%) Prior both 78 (60.0%) 0 0 0 20 (58.8%) 58 (92.1%) Prior either B7 - H4 expression, n (%) 103 (79.2%) 4 (57.1%) 10 (83.3%) 13 (92.9%) 27 (79.4%) 49 (77.8%) TPS status known 45 (43.7%) 3 (75.0%) 5 (50.0%) 7 (53.8%) 8 (29.6%) 22 (44.9%) High (TPS ≥70) 2 58 (56.3%) 1 (25.0%) 5 (50.0%) 6 (46.2%) 19 (70.4%) 27 (55.1%) Low (TPS <70) 27 (20.8%) 3 (42.9%) 2 (16.7%) 1 (7.1%) 7 (20.6%) 14 (22.2%) TPS not yet determined December 13, 2024 data cutoff
Safety and Tolerability
Safety Profile: Emi - Le Observed to be Generally Well Tolerated With No Grade 4 or 5 TRAEs 12 Note: Two Grade 5 treatment - emergent events, both deemed unrelated by the investigators (1 unrelated case of non - neutropenic sep sis in a patient with underlying inflammatory bowel disease, 1 respiratory failure related to progressive disease and occurring more than 30 days after last dose) * 7 treatment - related SAEs in 6 patients: troponin increase with negative workup for myocardial infarction (n=2, both G1), hemorrh agic cystitis with underlying uterine tract infection (n=1, G2), encephalopathy confounded by potential interaction between 2 concomitant medications (n=1, G3), hypersensitivity reaction reported in patien t a dmitted for managing pyrexia (n=1, G1), nausea (n=1, G2), nephrotic syndrome in patient with concurrent gout flare (n=1, G3, also shown as DLT) DLT, dose - limiting toxicity; G1, Grade 1; G2, Grade 2; G3, Grade 3; mg/m 2 , milligrams per meter squared Total (N=130) High Dose Range ≥76.2 mg/m 2 per cycle (N=38) Intermediate Dose Range 38.1 - 67.4 mg/m 2 per cycle (N=76) Subtherapeutic Dose Range <38.1 mg/m 2 per cycle (N=16) Patients with: 99 (76.2%) 31 (81.6%) 57 (75.0%) 11 (68.8%) Any treatment related adverse event (TRAE) 39 (30.0%) 14 (36.8%) 23 (30.3%) 2 (12.5%) Grade 3 TRAE 6 (4.6%) 1 (2.6%) 4 (5.3%) 1 (6.3%) Treatment - related serious adverse event (SAE)* 3 (2.3%) 0 2 (2.6%) 1 (6.3%) TRAE leading to treatment discontinuation 12 (9.2%) 3 (7.9%) 9 (11.8%) 0 TRAE leading to dose reduction 16 (12.3%) 8 (21.1%) 7 (9.2%) 1 (6.3%) TRAE leading to dose delay 0 0 0 0 TRAE leading to death December 13, 2024 data cutoff
Differentiated Safety Profile: Treatment - Related Adverse Events Observed in ≥10% of Patients 13 December 13, 2024 data cutoff High Dose Range ≥76.2 mg/m 2 per cycle (N=38) Intermediate Dose Range 38.1 – 67.4 mg/m 2 per cycle (N=76) All Doses (N=130) Percentage (%) of Patients (N=130) (N=76) (N=38) All Doses 38.1 - 67.4 mg/m2 >76.2 mg/m2 53 42 39 29 18 16 13 13 11 11 11 8 8 8 8 5 5 0 10 20 30 40 50 60 70 80 90 100 Percentage (%) of Patients 21 16 5 3 G3 G1-2 34 26 26 29 8 8 17 9 13 16 5 12 11 11 13 11 11 0 10 20 30 40 50 60 70 80 90 100 Percentage (%) of Patients 12 1 7 1 5 38 29 31 28 10 9 15 10 12 13 7 10 8 8 10 8 8 0 10 20 30 40 50 60 70 80 90 100 Percentage (%) of Patients 14 1 9 2 2 4 Headache Amylase increased Platelet count decreased Hypophosphataemia Constipation ALP increased Arthralgia Anaemia ALT increased Diarrhoea Decreased appetite Vomiting Pyrexia Fatigue Proteinuria Nausea AST increased Note: In addition to the Grade 2 hemorrhagic cystitis noted on the previous slide, there were only 3 other bleeding events (a ll Grade 1) assessed as possibly treatment related. ALT, alanine aminotransferase; ALP, alkaline phosphatase; AST, aspartate aminotransferase; mg/m 2 , milligrams per meter squared Grade 1 or 2 Grade 3
Clinical Activity Data
c c c c cc u c c u -100 -80 -60 -40 -20 0 20 40 60 80 100 120 B e s t C h a n g e i n T a r g e t L e s i o n S i z e f r o m B a s e l i n e ( % ) TPS Not Yet Determined (N=12) TPS >70 (N=40) TPS <70 (N=44) <38.1 mg/m2 38.1 - 67.4 mg/m2 >76.2 mg/m2 (N=14) (N=61) (N=21) Notes: a) Evaluable population (N=96) consists of patients with measurable disease at baseline and at least one post - baseline sc an. Of the 130 patients in the safety population, 18 did not have measurable disease at baseline or were ongoing without a post - baseline scan, and 16 (including 1 B7 - H4 high ovarian cancer patient in the Intermediate Dose Range and 1 B7 - H4 high TNBC patient in the High Dose Range) discontinued prior to first scan. b) 4 TNBC patients in the Intermediate Dose Range and 1 TNBC patient in the High Dose Range were among the 12 pat ients with B7 - H4 expression not yet determined. c) Missing from waterfall but included in the evaluable population (N=96) are 5 patients with progressive disease as best response who had a post - treatment sc an but not post - baseline measurement of their target lesion. 1 of these patients with TNBC was treated in the Intermediate Dose Range and was B7 - H4 high. mg/m 2 , milligrams per meter squared; TNBC, triple - negative breast cancer Clinical Activity in Evaluable Patients Correlated With Both Dose and B7 - H4 Expression 15 December 13, 2024 data cutoff High Dose Range ≥76.2 mg/m 2 per cycle (N=21) Intermediate Dose Range 38.1 – 67.4 mg/m 2 per cycle (N=61) Subtherapeutic Dose Range <38.1 mg/m 2 per cycle (N=14) * = Ongoing treatment C = Confirmed responder U = Ongoing unconfirmed responder Best Change in Target Lesion Size from Baseline (%) B7 - H4 low (N=44) B7 - H4 high (N=40) Expression not yet determined (N=12)
Emi - Le Shown to be Clinically Active in Heavily Pretreated Patients 16 Dose Range Known B7 - H4 Expression Subtherapeutic <38.1 mg/m 2 per cycle High ≥76.2 mg/m 2 per cycle Responses/Evaluable Patients with Known B7 - H4 Status (ORR%) Intermediate 38.1 – 67.4 mg/m 2 per cycle B7 - H4 Low B7 - H4 High 0/7 (0%) 0/5 (0%) 0/9 (0%) 0/28 (0%) 2/9 (22% Confirmed ORR); 7/9 (78%) with ≥30% Tumor Reductions in Target Lesions 6/26 (23% Confirmed ORR); 9/26 (35%) with ≥30%Tumor Reductions in Target Lesions December 13, 2024 data cutoff mg/m 2 , milligrams per meter squared; ORR, objective response rate per RECIST version 1.1
0 4 8 12 16 20 24 28 Weeks -100 -80 -60 -40 -20 0 20 40 60 80 100 120 % C h a n g e i n S u m o f T a r g e t L e s i o n D i a m e t e r s ACC-I (N=3) Ovarian (N=3) Endo (N=4) HR+BC (N=3) TNBC (N=13) Intermediate Dose Range: Encouraging Clinical Activity in Evaluable Patients With B7 - H4 High Tumors 17 December 13, 2024 data cutoff PR PR PR PR PR PR -100 -80 -60 -40 -20 0 20 40 60 80 100 120 B e s t C h a n g e i n T a r g e t L e s i o n S i z e f r o m B a s e l i n e ( % ) ACC-I (N=3) Ovarian (N=3) Endo (N=4) HR+BC (N=3) TNBC (N=13) * = treatment ongoing Note: Missing from Intermediate Dose Range waterfall, but included in response rate denominator, is one TNBC patient with pro gre ssive disease as best response who had a post - treatment scan but not post - baseline measurement of their target lesion 1. Bardia et al. NEJM 2021 April 22; 384(16): 1529 - 1541 ACC - 1, a denoid cystic c arcinoma – type 1; Endo, endometrial cancer; HR+BC , hormone - receptor - positive, human e pidermal growth f actor r eceptor 2 negative metastatic breast cancer; m g/m 2 , milligrams per meter squared; ORR, objective response rate per RECIST version 1.1; PR, confirmed partial response; TNBC, triple - negative breast cancer 23% Confirmed ORR (6/26 patients) 35% with ≥30%Tumor Reductions in Target Lesions (9/26 patients) ASCENT Phase 3 clinical trial of sacituzumab govitecan showed a median PFS of ~7 weeks for standard of care single - agent chemo in relapsed/refractory TNBC 1 arrows = treatment ongoing
T T T T T T T TT TT TT T T 3 5 4 5 4 5 4 4 5 4 5 4 PR PR PR -100 -80 -60 -40 -20 0 20 40 60 80 100 120 B e s t C h a n g e i n T a r g e t L e s i o n S i z e f r o m B a s e l i n e ( % ) Intermediate Dose Range: Encouraging Clinical Activity in Evaluable Patients With B7 - H4 High TNBC 18 December 13, 2024 data cutoff 23% Confirmed ORR (3/13 patients) T = Previously treated with one topoisomerase - 1 inhibitor ADC TT = Previously treated with more than one topoisomerase - 1 inhibitor ADC Missing from Intermediate Dose Range waterfall, but included in response rate denominator, is one TNBC patient with 8 prior l ine s and progressive disease as best response who had a post - treatment scan but not post - baseline measurement of their target lesion 1. Bardia et al. NEJM 2021 April 22; 384(16): 1529 - 1541 ADC, antibody - drug conjugate; mg/m 2 , milligrams per meter squared; ORR, objective response rate per RECIST version 1.1 ; PR, confirmed partial response; Q4W, dosing once every four weeks; TNBC, triple - negative breast cancer; t opo - 1, topoisomerase - 1 inhibitor * = treatment ongoing • Encouraging activity in a heavily pretreated patient population – ORR of only ~5% for standard of care single - agent chemo in relapsed/refractory TNBC 1 • Expansion initiated at 67.4 mg/m 2 Q4W (high end of Intermediate Dose Range) in patients with TNBC who have received 1 - 4 prior lines, including at least one topo - 1 ADC – Dose observed to be well tolerated in patients across tumor types – All 4 evaluable patients across B7 - H4 high tumors at this dose had reductions in target lesions and were on study with treatment durations of ~16 weeks or more as of data cutoff # of prior lines Prior topo - 1 ADC(s)
Expansion Enrollment Now Underway at 67 mg/m 2 Q4W in Post - Topo - 1 TNBC 19 Primary Objectives: Assess safety, tolerability and preliminary antitumor activity Secondary Objectives: Assess PK and ADA • Advanced or metastatic TNBC • 1 to 4 prior lines of treatment, including at least one prior topo - 1 ADC • ER - , PR - , HER2 - based on local testing of their most recent biopsy as defined in ASCO/CAP guidelines o Patients with HR+BC at diagnosis permitted o Patients with HER2 IHC 0, IHC 1, or IHC 2/ISH negative permitted • Patients stratified by B7 - H4 expression status Dose A: 67.4 mg/m 2 Q4W Dose B: TBD Dose A: 67.4 mg/m 2 Q4W Dose B: TBD Stage 1 Stage 2 Select Dose and Biomarker Cutoff for Potential Pivotal Trial ACC - 1, a denoid cystic c arcinoma – type 1; ADA, anti - drug antibody; ADC, antibody - drug conjugate; ASCO/CAP, American Society of Clinical Oncology and the College of American Pathologists; ER - , est rogen receptor negative; HER2 - , human e pidermal growth f actor r eceptor 2 negative; HR+/HER2 - BC, hormone - receptor - positive, human e pidermal growth f actor r eceptor 2 negative breast cancer; IHC, immunohistochemistry; ISH, in situ hybridization; mg/m 2 , milligrams per meter squared; PK, pharmacokinetics; PR - , progesterone receptor negative; Q4W, dosing every four weeks; TNBC, triple - negative breast c ancer; topo - 1, topoisomerase - 1 inhibitor Enrollment Criteria Additional cohorts in other tumor types (HR+BC, endometrial, ovarian, ACC - 1) included in protocol
High Dose Range: Preliminary Data S uggest P otential for Even Greater Clinical Activity 20 December 13, 2024 data cutoff The two patients above with unconfirmed partial responses ( uPRs ) progressed upon their confirmatory scans following the data cutoff. 1. Bardia et al. NEJM 2021 April 22; 384(16): 1529 - 1541 HR+BC, hormone - receptor - positive, human e pidermal growth f actor r eceptor 2 negative metastatic breast cancer; ORR, objective response rate per RECIST version 1.1 ; TNBC, triple - negative breast cancer uPR PR CR uPR -100 -80 -60 -40 -20 0 20 40 60 80 100 120 B e s t C h a n g e i n T a r g e t L e s i o n S i z e f r o m B a s e l i n e ( % ) Ovarian (N=1) HR+BC (N=4) TNBC (N=4) >=76.2 mg/m2 (N=9) * = treatment ongoing 22% Confirmed ORR (2/9 patients) 78% with ≥30% Tumor Reductions in Target Lesions (7/9 patients) Patients who did not confirm had protocol - mandated dose delays for proteinuria lab values prior to their confirmatory scans • Proteinuria is generally asymptomatic and reversible – Appears to be payload - related; seen with other some auristatin ADCs – Primarily albuminuria, with limited impact on serum albumin or serum creatinine – Implementing mitigation strategies (e.g., ACEi /ARB prophylaxis) to reduce dose delays Evaluable Patients with B7 - H4 High Tumors
• 1H2025: Continue expansion enrollment at 67.4 mg/m 2 Q4W in TNBC patients who have previously received at least one topo - 1 ADC • 2025: Initiate expansion enrollment at second dose in post - topo - 1 TNBC • 2025: Present additional Phase 1 dose escalation and backfill cohort clinical data • Continue to support internal pipeline and existing collaborations with Johnson & Johnson and Merck KGaA, Darmstadt, Germany • 2025: Present initial clinical pharmacodynamic STING activation data Expected 2025 Milestones and Areas of Focus 21 XMT - 2056: Lead Immunosynthen Product Candidate Emi - Le: Lead Dolasynthen Product Candidate ADC, antibody - drug conjugate; mg/m 2 , milligrams per meter squared; Q4W, dosing every four weeks; TNBC, triple - negative breast cancer; topo - 1, topoisomerase - 1 inhib itor Pipeline
Q&A Session Thank you to the patients, families, caregivers and investigators who are participating in this clinical trial 22
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Mersana Therapeutics (NASDAQ:MRSN)
Gráfica de Acción Histórica
De Dic 2024 a Ene 2025
Mersana Therapeutics (NASDAQ:MRSN)
Gráfica de Acción Histórica
De Ene 2024 a Ene 2025
