emiltatug ledadotin (XMT-1660) / Mersana - LARVOL DELTA

Initial phase 1 dose escalation data for emiltatug ledadotin (Emi-Le), a novel B7-H4-directed dolasynthen antibody-drug conjugate. (ASCO 2025) - P1 | "Emi-Le (XMT-1660) is a B7-H4-directed Dolasynthen ADC designed with a proprietary auristatin F-HPA microtubule inhibitor payload with controlled bystander effect... Based on the initial reported data, Emi-Le appears to have encouraging clinical activity and tolerability in a heavily pretreated population. Further clinical development is ongoing in the EXP portion of the trial at a dose of 67.4 mg/m2 Q4W in pts with advanced/metastatic TNBC who have received 1-4 prior lines of systemic therapy, including at least one topo-1 ADC. Dose exploration is ongoing to identify a potential second higher EXP dose."

P1 data • Adenoid Cystic Carcinoma • Fatigue • Interstitial Lung Disease • Neutropenia • Oncology • Optic Neuritis • Pain • Pulmonary Disease • Renal Disease • Respiratory Diseases • Thrombocytopenia • Triple Negative Breast Cancer • HER-2 • VTCN1

Emiltatug ledadotin (Emi-Le): A B7-H4-directed dolasynthen antibody-drug conjugate (ADC) being investigated in phase 1 dose expansion in patients with triple negative breast cancer who received at least one prior topoisomarase-1 inhibitor ADC. (ASCO 2025) - P1 | "Emiltatug ledadotin (Emi-Le; XMT-1660) is a B7-H4-directed Dolasynthen ADC designed with a precise, target-optimized drug-to-antibody ratio (DAR 6) and a proprietary auristatin F-HPA microtubule inhibitor payload with controlled bystander effect...The protocol includes the option for multiple additional indications, including HR+/HER2- breast cancer, endometrial cancer, ovarian cancer, and ACC-1. NCT05377996"

Clinical • P1 data • Breast Cancer • Endometrial Cancer • HER2 Breast Cancer • HER2 Negative Breast Cancer • HER2 Positive Breast Cancer • Oncology • Ovarian Cancer • Solid Tumor • Triple Negative Breast Cancer • HER-2 • VTCN1

Mersana Therapeutics Reports Additional Positive Interim Phase 1 Clinical Data for Emi-Le in Oral Presentation at 2025 ASCO Annual Meeting (GlobeNewswire) - P1 | N=319 | NCT05377996 | Sponsor: Mersana Therapeutics | "Safety and tolerability as of the March 8, 2025 data cut-off were consistent with initial data previously reported in January 2025, and no new safety signals were observed....31% confirmed objective response rate (ORR) (8/26) across all enrolled tumor types with B7-H4 high tumor expression (defined as a tumor proportion score of 70% or higher) receiving intermediate Emi-Le doses (38.1 milligrams per meter squared (mg/m2) to 67.4 mg/m2 per cycle)....56% ORR (5/9, including one unconfirmed response as of the March 8, 2025 data cut-off that was subsequently confirmed) in ACC-1 regardless of dose and B7-H4 expression. Among all ACC-1 patients who were enrolled in the Phase 1 clinical trial, the median progression free survival (PFS) had not yet been reached as of the March 8, 2025 data cut-off."

P1 data • Adenoid Cystic Carcinoma • Endometrial Cancer • Hormone Receptor Positive Breast Cancer • Ovarian Cancer • Triple Negative Breast Cancer

CORRECTION - Mersana Therapeutics Provides Business Update and Announces First Quarter 2025 Financial Results (GlobeNewswire) - "Mersana continues to advance the dose expansion portion of its Phase 1 clinical trial of Emi-Le in patients with TNBC who have received one to four prior lines of therapy, including at least one topo-1 ADC. In recent months, the company has made significant progress in the enrollment of patients in its 'Dose A' cohort, in which patients are receiving 67.4 mg/m² of Emi-Le every four weeks (Q4W)...Mersana also recently initiated enrollment in its 'Dose B' cohort. These patients are receiving a starting dose of 44.5 mg/m2 of Emi-Le on days 1 and 8 of the first four-week cycle followed by 80 mg/m2 of Emi-Le Q4W...The company plans to report initial clinical data from the expansion portion of its Phase 1 clinical trial in the second half of 2025...Mersana plans to continue enrolling patients in dose escalation and expects to present initial clinical pharmacodynamic STING activation data for XMT-2056 in 2025."

P1 data • Trial status • Solid Tumor • Triple Negative Breast Cancer • HER-2

Updated Clinical Data Presented at ESMO Breast Cancer 2025 Today (GlobeNewswire) - P1 | N=319 | NCT05377996 | Sponsor: Mersana Therapeutics | "Earlier this morning at the European Society for Medical Oncology Breast Cancer 2025 Annual Congress...updated clinical data as of a March 8, 2025 data cutoff from Emi-Le’s Phase 1 dose escalation and backfill cohorts were presented...The presentation included clinical activity data among evaluable patients (those with measurable disease at baseline and at least one post-baseline scan) across all tumor types (TNBC, hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2) negative breast cancer; ovarian cancer; endometrial cancer and adenoid cystic carcinoma type 1) with B7-H4 high tumor expression (defined as a tumor proportion score of 70% or higher) who received intermediate Emi-Le doses of 38.1 milligrams per meter squared (mg/m2) to 67.4 mg/m2 per cycle. For these patients, the confirmed objective response rate (ORR) was 31% (8 of 26 patients)."

P1 data • Endometrial Cancer • HER2 Negative Breast Cancer • Hormone Receptor Positive Breast Cancer • Ovarian Cancer • Triple Negative Breast Cancer

Clinical activity of emiltatug ledadotin (Emi-Le), a B7-H4-directed ADC, in patients with TNBC who received at least one prior topoisomerase-1 inhibitor (Topo-1) ADC (ESMO-BC 2025) - P1 | "Based on the initial reported data, Emi-Le appears to have encouraging clinical activity and tolerability in a heavily pretreated TNBC population with high B7-H4 expression who had previously received topo-1 ADCs. Further clinical development of Emi-Le is ongoing in the expansion portion of the Ph1 trial at a dose of 67.4 mg/m2 Q4W in pts with advanced/metastatic TNBC who have received 1-4 prior lines of systemic therapy, including at least one topo-1 ADC."

Clinical • Triple Negative Breast Cancer • VTCN1

Mersana Therapeutics Announces Strategic Restructuring and Reprioritization Plan Focused on Advancing Emi-Le in Triple-Negative Breast Cancer (GlobeNewswire) - "Mersana Therapeutics, Inc...announced the implementation of a strategic restructuring and reprioritization plan aimed at extending the company’s cash runway and furthering the development of emiltatug ledadotin (Emi-Le; XMT-1660), the company’s B7-H4-directed Dolasynthen ADC...Mersana’s strategic restructuring and reprioritization plan will reduce the company’s workforce by approximately 55% across functions. The workforce reduction is expected to be substantially complete by the end of the third quarter of 2025...The company will also reduce its research activities and eliminate its internal pipeline development efforts. In the near term, Mersana will focus Emi-Le development efforts on breast cancer to enable the generation of additional safety, tolerability and clinical activity data. Mersana plans to continue supporting its Phase 1 dose escalation work for XMT-2056 and its ongoing collaborations....Collectively, these actions..."

Pipeline update • Solid Tumor

Mersana Therapeutics Announces Upcoming Emi-Le Oral and Poster Presentations at ASCO 2025 Annual Meeting (GlobeNewswire) - "Mersana Therapeutics, Inc...today announced that the following presentations related to emiltatug ledadotin (Emi-Le; XMT-1660), Mersana’s B7-H4-directed Dolasynthen ADC, will be given at the American Society of Clinical Oncology (ASCO) 2025 Annual Meeting taking place May 30-June 3, 2025 at McCormick Place, Chicago, IL."

Clinical data • Triple Negative Breast Cancer

Mersana Therapeutics Announces Upcoming Oral Presentation of Emi-Le Clinical Data at European Society for Medical Oncology (ESMO) Breast Cancer 2025 Annual Congress (GlobeNewswire) - "Mersana Therapeutics, Inc...announced that Phase 1 dose escalation and backfill cohort clinical data for emiltatug ledadotin (Emi-Le; XMT-1660) will be presented in an oral session at the ESMO Breast Cancer 2025 Annual Congress, which is being held from May 14-17, 2025, in Munich, Germany."

P1 data • Triple Negative Breast Cancer

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2024 Financial Results (GlobeNewswire) - "Emiltatug Ledadotin: In 2025, Mersana plans to initiate expansion enrollment at a second dose in patients with TNBC who have received one to four prior lines of treatment, including at least one prior topo-1 ADC. The company also plans to present additional Phase 1 clinical data from dose escalation and backfill cohorts in 2025."

P1 data • Trial status • Triple Negative Breast Cancer

Mersana Therapeutics Announces Additional FDA Fast Track Designation Granted to Emiltatug Ledadotin (XMT-1660) (GlobeNewswire) - "Mersana Therapeutics, Inc...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."

Commercial • Evidence highlight • Fast track • Hormone Receptor Positive Breast Cancer • Triple Negative Breast Cancer • HER-2

Mersana’s Expected 2025 Milestones and Areas of Focus (GlobeNewswire) - "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."

Clinical data • Enrollment status • P1 data • Triple Negative Breast Cancer

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 (GlobeNewswire) - P1 | N=319 | NCT05377996 | Sponsor: Mersana Therapeutics | "Emi-Le was observed to be generally well tolerated, with no Grade 4 or 5 treatment-related adverse events (TRAEs) reported....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....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."

P1 data • Trial status • Adenoid Cystic Carcinoma • Endometrial Cancer • Fallopian Tube Cancer • Ovarian Cancer • Peritoneal Cancer • Triple Negative Breast Cancer

Mersana Therapeutics Provides Business Update and Announces Third Quarter 2024 Financial Results (GlobeNewswire) - "Recent Accomplishments, Strategic Priorities and Expected Milestones - XMT-1660: Mersana continues to advance its Phase 1 clinical trial of XMT-1660....The dose escalation portion of the trial is ongoing, with the company having recently escalated to a dose of 115 milligrams per meter squared administered every four weeks. A maximum tolerated dose has not yet been established. Approximately 75 percent of the patients that have been enrolled in the trial to date have triple-negative breast cancer (TNBC) or hormone receptor-positive breast cancer (HR+BC)....Last week at World ADC 2024, Mersana presented new preclinical data demonstrating XMT-1660’s anti-tumor activity following topo-1 treatment. By the end of 2024, Mersana plans both to share initial safety, tolerability, efficacy and biomarker data from its Phase 1 dose escalation and backfill cohorts at a company event and to initiate the expansion portion of the trial in patients with TNBC..."

P1 data • Preclinical • Trial status • Hormone Receptor Positive Breast Cancer • Triple Negative Breast Cancer

Mersana Therapeutics Provides Business Update and Announces First Quarter 2024 Financial Results (GlobeNewswire) - "XMT-1660: Mersana plans to share initial dose escalation and backfill cohort data and initiate the expansion portion of the trial in the second half of 2024."

P1 data • Oncology • Solid Tumor

XMT-1660: A phase I, first-in-human trial of a B7-H4-directed dolasynthen antibody-drug conjugate in ovarian, endometrial, and breast cancers (SGO 2024) - P1 | "The trial is currently enrolling patients. NCT05377996"

P1 data • Breast Cancer • Oncology • Solid Tumor • Triple Negative Breast Cancer • VTCN1

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2023 Financial Results (GlobeNewswire) - "Mersana continues to advance its Phase 1 clinical trial of XMT-1660, the company’s lead Dolasynthen ADC candidate targeting B7-H4....Mersana plans to initiate tumor-specific expansion cohorts in the second quarter of 2024 and expects to share initial dose escalation and backfill cohort data in mid-2024....Mersana is restarting its Phase 1 clinical trial of XMT-2056, the company's lead Immunosynthen ADC candidate targeting a novel HER2 epitope....Mersana plans to advance dose escalation of this wholly owned product candidate in 2024."

Trial status • Adenoid Cystic Carcinoma • Breast Cancer • Endometrial Cancer • Fallopian Tube Cancer • Gynecologic Cancers • Oncology • Ovarian Cancer • Peritoneal Cancer • Solid Tumor • Triple Negative Breast Cancer

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2023 Financial Results (GlobeNewswire) - "At the European Society of Gynaecological Oncology (ESGO) 2024 Congress from March 7-10, 2024 in Barcelona, Spain, clinical data will be presented for Mersana’s two discontinued NaPi2b ADC product candidates: XMT-1536 (UpRi), which was developed using the company’s first-generation Dolaflexin ADC platform, and XMT-1592, which was developed using the company’s next-generation Dolasynthen ADC platform....The decline in R&D expenses was primarily related to reduced manufacturing and clinical costs related to UpRi and XMT-2056 and manufacturing costs for the company’s Dolasynthen platform, partially offset by increased clinical costs related to XMT-1660."

Clinical data • Commercial • Oncology • Solid Tumor

A Study of XMT-1660 in Participants With Solid Tumors (clinicaltrials.gov) - P1 | N=319 | Recruiting | Sponsor: Mersana Therapeutics | N=166 ➔ 319 | Trial completion date: Jan 2026 ➔ May 2027 | Trial primary completion date: Jan 2025 ➔ Dec 2026

Enrollment change • Trial completion date • Trial primary completion date • Adenoid Cystic Carcinoma • Breast Cancer • Endometrial Cancer • Fallopian Tube Cancer • Oncology • Ovarian Cancer • Solid Tumor • Triple Negative Breast Cancer

Mersana Therapeutics Announces Business Updates, Expected 2024 Milestones and Upcoming Presentation at the 42nd Annual J.P. Morgan Healthcare Conference (GlobeNewswire) - "XMT-1660: Mersana continues to advance its Phase 1 clinical trial of XMT-1660, the company’s lead Dolasynthen ADC candidate targeting B7-H4...Mersana plans to initiate tumor-specific expansion cohorts in the second quarter of 2024 and share initial dose escalation and backfill cohort data in mid-2024...XMT-2056: Mersana is restarting its Phase 1 clinical trial of XMT-2056...The company plans to advance dose escalation in 2024....In the first half of 2024, Mersana expects to present data at multiple scientific meetings demonstrating Dolasynthen’s differentiation from first-generation cytotoxic ADC platforms. The presentations will include clinical data from two discontinued ADC candidates, XMT-1592 and XMT-1536 (UpRi)."

Clinical data • P1 data • Trial status • Oncology • Solid Tumor

A Study of XMT-1660 in Participants With Solid Tumors (clinicaltrials.gov) - P1 | N=166 | Recruiting | Sponsor: Mersana Therapeutics

Trial completion date • Trial primary completion date • Breast Cancer • Endometrial Cancer • Fallopian Tube Cancer • Oncology • Ovarian Cancer • Solid Tumor • Triple Negative Breast Cancer

Mersana Therapeutics Provides Business Update and Announces Third Quarter 2023 Financial Results (GlobeNewswire) - ".Additionally, we are now preparing to resume enrollment in our Phase 1 clinical trial of XMT-2056, a novel HER2-directed STING-agonist ADC product candidate....Advance XMT-1660 and Mersana’s Dolasynthen Platform: Mersana expects to complete the dose escalation portion of this Phase 1 clinical trial by the end of 2023 and initiate the dose expansion portion of the trial in 2024."

Trial status • Oncology • Solid Tumor

Mersana Therapeutics Announces Second Quarter 2023 Financial Results (GlobeNewswire) - "Advance XMT-1660 and Dolasynthen Platform: Mersana expects to complete the dose escalation portion of its Phase 1 clinical trial of this candidate in 2023 and initiate the dose expansion portion of the trial in 2024."

Trial status • Breast Cancer • Endometrial Cancer • Fallopian Tube Cancer • Gynecologic Cancers • Oncology • Ovarian Cancer • Peritoneal Cancer • Solid Tumor

Discovery and Preclinical Characterization of XMT-1660, an Optimized B7-H4-Targeted Antibody-Drug Conjugate for the Treatment of Cancer. (PubMed, Mol Cancer Ther) - P1 | "In a panel of 28 breast cancer patient-derived xenografts (PDX), XMT-1660 demonstrated activity that correlated with B7-H4 expression. XMT-1660 has recently entered clinical development in a Phase 1 study (NCT05377996) in cancer patients."

IO biomarker • Journal • Preclinical • Breast Cancer • Endometrial Cancer • Immune Modulation • Oncology • Ovarian Cancer • Solid Tumor • VTCN1

XMT-1660: A phase 1b trial of a B7-H4 targeted antibody drug conjugate (ADC) in breast, endometrial, and ovarian cancers. (ASCO 2023) - P1 | "XMT-1660 is a B7-H4-directed Dolasynthen antibody drug conjugate designed with a precise, optimized drug-to-antibody ratio and a DolaLock microtubule inhibitor payload with controlled bystander effect. NCT05377996. Clinical trial information: NCT05377996."

P1 data • Breast Cancer • HER2 Breast Cancer • Oncology • Ovarian Cancer • Solid Tumor • Triple Negative Breast Cancer • CDK4 • ER • HER-2 • VTCN1