Trabectedin Research Articles

Abstract 1880: Ecubectedin and PM54 demonstrate antitumor activity in patient-derived xenograft models of soft tissue sarcoma

Abstract Objective: Soft tissue sarcoma (STS) is a heterogenous group of rare, malignant tumors arising from mesenchymal tissue. Doxorubicin (DOX)-based chemotherapy is the standard for advanced or metastatic STS, despite low response rates and poor disease control. We explored the antitumor activity of two novel compounds, ecubectedin (ECU; PM14) and PM54 (PharmaMar), in two patient-derived xenograft (PDX) models of STS, leiomyosarcoma (LMS) and CIC-rearranged sarcoma (CRS). Mode of action of ECU and PM54 is similar to lurbinectedin (LUR), inhibiting oncogenic transcription by eviction of oncogenic transcription factors from gene promotors’ recognition sequences, while inducing the generation of double strand breaks through DNA adduct formation. Methods: Female NMRI nu/nu mice (n=104) were transplanted bilaterally with STS PDX: UZLX-STS134 (CRS) and UZLX-STS22_2 (LMS). Xenografted mice were randomized to six treatment groups: 1) vehicle (VEH) (5% dextrose) 5 mL/kg once weekly (QW) intravenously (IV); 2) DOX 5 mg/kg QW IV; 3) trabectedin (TRA) 0.15 mg/kg QW IV; 4) LUR 0.18 mg/kg QW IV; 5) ECU 1.2 mg/kg QW IV; 6) PM54 1.2 mg/kg QW IV. Treatment lasted 16 days and antitumor activity was assessed by tumor volume (TV) analysis, histopathology and western blot. The Mann-Whitney U test was used to compare groups, the Wilcoxon test to compare to baseline. Results: ECU and PM54 caused TV shrinkage in UZLX-STS134, while TV in other groups grew significantly on day 16 (Table 1). VEH treatment led to the largest TV increase on day 16, compared to any treatment. PM54 treatment showed TV stabilization in UZLX-STS22_2, and significantly smaller tumors than VEH and TRA treated tumors (p<0.05 and p<0.01, respectively). Histopathological evaluation corroborate the results from the relative TV analysis. Conclusion: Novel drugs exhibit promising results in the PDX models tested, supporting ongoing exploration in additional PDX models of synovial sarcoma and dedifferentiated liposarcoma. Table 1: TV change on day 16 versus baseline, and comparison of proliferative and apoptotic activity Tumor volume change Proliferative activity (pHH3) Apoptotic activity (cPARP) Subtypes UZLX-STS134 UZLX-STS22_2 UZLX-STS134 UZLX-STS22_2 UZLX-STS134 UZLX-STS22_2 VEH(5 ML/kg) 387%*** 349%** n/a n/a n/a n/a DOX (5 mg/kg/QW IV) 177%*** 243%** ↓*** ↓ ↑** ↑ TRA(0.15 mg/kg/QW IV) 230%** 254%*** ↓** ↓** ↑** ↑*** LUR(0.18 mg/kg/QW IV) 202%** 232%** ↓*** ↓*** ↑*** ↑** ECU(1.2 mg/kg/QW IV) 41%*** 181%** ↓*** ↓*** ↑*** ↑*** PM54 (1.2 mg/kg/QW IV) 76%*** 162% ↓*** ↓*** ↑*** ↑ Citation Format: Daniël Gorgels, Agnieszka Wozniak, Chao-Chi Wang, Pablo M. Avilés, Maria J. Guillen, Carmen Cuevas, Patrick Schöffski. Ecubectedin and PM54 demonstrate antitumor activity in patient-derived xenograft models of soft tissue sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1880.

Trabectedin and Lurbinectedin Modulate the Interplay between Cells in the Tumour Microenvironment-Progresses in Their Use in Combined Cancer Therapy.

Trabectedin (TRB) and Lurbinectedin (LUR) are alkaloid compounds originally isolated from Ecteinascidia turbinata with proven antitumoral activity. Both molecules are structural analogues that differ on the tetrahydroisoquinoline moiety of the C subunit in TRB, which is replaced by a tetrahydro-β-carboline in LUR. TRB is indicated for patients with relapsed ovarian cancer in combination with pegylated liposomal doxorubicin, as well as for advanced soft tissue sarcoma in adults in monotherapy. LUR was approved by the FDA in 2020 to treat metastatic small cell lung cancer. Herein, we systematically summarise the origin and structure of TRB and LUR, as well as the molecular mechanisms that they trigger to induce cell death in tumoral cells and supporting stroma cells of the tumoral microenvironment, and how these compounds regulate immune cell function and fate. Finally, the novel therapeutic venues that are currently under exploration, in combination with a plethora of different immunotherapeutic strategies or specific molecular-targeted inhibitors, are reviewed, with particular emphasis on the usage of immune checkpoint inhibitors, or other bioactive molecules that have shown synergistic effects in terms of tumour regression and ablation. These approaches intend to tackle the complexity of managing cancer patients in the context of precision medicine and the application of tailor-made strategies aiming at the reduction of undesired side effects.

Immunometabolic actions of trabectedin and lurbinectedin on human macrophages: relevance for their anti-tumor activity.

In recent years, the central role of cell bioenergetics in regulating immune cell function and fate has been recognized, giving rise to the interest in immunometabolism, an area of research focused on the interaction between metabolic regulation and immune function. Thus, early metabolic changes associated with the polarization of macrophagesinto pro-inflammatoryorpro-resolving cells under different stimuli have been characterized. Tumor-associated macrophages are among the most abundant cells in the tumor microenvironment; however, it exists an unmet need to study the effect of chemotherapeutics on macrophage immunometabolism. Here, we use a systems biology approach that integrates transcriptomics and metabolomics to unveil the immunometabolic effects of trabectedin (TRB) and lurbinectedin (LUR), two DNA-binding agents with proven antitumor activity. Our results show that TRB and LUR activate human macrophages toward a pro-inflammatory phenotype by inducing a specific metabolic rewiring program that includes ROS production, changes in the mitochondrial inner membrane potential, increased pentose phosphate pathway, lactate release, tricarboxylic acids (TCA) cycle, serine and methylglyoxal pathways in human macrophages. Glutamine, aspartate, histidine, and proline intracellular levels are also decreased, whereas oxygen consumption is reduced. The observed immunometabolic changes explain additional antitumor activities of these compounds and open new avenues to design therapeutic interventions that specifically target the immunometabolic landscape inthe treatment of cancer.

Trabectedin suppresses osteosarcoma pulmonary metastasis in a mouse tumor xenograft model.

Osteosarcoma (OS) is the most common primary bone tumor that mainly affects adolescents and young adults. Although standard treatment modality can achieve up to 60%-70% 5-year survival rate, there has not been any substantial improvement over the past four decades. Furthermore, those presenting with pulmonary metastatic lesions often undergo a highly unfavorable clinical course. Therefore, there is a severely unmet clinical need to provide a more effective treatment for patients with OS. In this study, we show that trabectedin (TBD), a chemotherapeutic agent approved for soft tissue sarcomas, significantly suppresses pulmonary metastasis in a mouse OS xenograft model. In vitro experiments revealed that TBD suppresses cell migration potentially by downregulating the activity of ERK1/2, intracellular molecules that are critically involved in the regulation of cell motility. Collectively, our data may provide a basis for further investigation of TBD on the potential use for OS patients who are at great risk of pulmonary metastasis.

A Prolonged Response and Characteristics of Trabectedin Treatment of Metastatic Soft Tissue Sarcoma

Unique features and treatment effects of trabectedin are presented in consideration of soft tissue sarcoma management. A prolonged time on trabectedin through 59 cycles is shown. This is one of the longer reported uses of trabectedin successfully to control disease. Adjunctive cytoreduction options with surgery, radiation or ablation are presented. Future studies would be helpful to investigate treatment holidays, the impact of multi-modality care and assessment of genetics of clonal metastases. This may assist in guiding and selecting patients for priority treatment with trabectedin. J Med Cases. 2021;12(4):160-163 doi: https://doi.org/10.14740/jmc3655

Research Advances in Synthesis of Trabectedin

Research Advances in Synthesis of Trabectedin

Abstract 1661: Temozolomide suppresses a doxorubicin resistant follicular dendritic cell sarcoma in a patient derived orthotopic xenograft mouse model

Abstract Introduction: Follicular dendritic cell sarcoma (FDCS) is a very rare and highly refractory soft tissue sarcoma. The CHOP chemotherapy has been used as systemic therapy for FDCS, which includes cyclophosphamide, doxorubicin (DOX), vincristine, and prednisolone. However, FDCS has poor clinical outcome even though CHOP therapy was administered. A FDCS patient tumor was previously implanted orthotopically in the biceps femoris of nude mice to establish a patient-derived orthotopic xenograft (PDOX) model in our laboratory at AntiCancer Inc. The FDCS patient had resistance to DOX in clinical setting. We previously found the FDCS PDOX model had resistance to DOX as well as clinical settings. In the present study, we evaluated the efficacy of temozolomide (TMZ), trabectedin (TRAB), and pazopanib (PAZ) on the DOX resistant FDCS PDOX model. Methods: The FDCS PDOX mouse model was established and randomized into five groups of eight mice, respectively. Group 1, Control (Ctrl) treated with PBS, i.p.; Group 2, DOX, 2.4 mg/kg, i.p., weekly; Group 3, PAZ, 50 mg/kg, oral gavage, daily; Group 4, TRAB, 0.15 mg/kg, i.v., weekly; Group 5, TMZ, 25 mg/kg, oral gavage, daily. Treatment term was for 2 weeks. Treatment efficacy was evaluated based on tumor volume ratio (tumor volume after treatment relative to tumor volume at the beginning of treatment) and histopathology. Adverse event was evaluated based on body weight ratio. Tumor volume and body weight were assessed 2 times per week. Results: Tumor volume ratio was the Ctrl group: 11.35±4.50, DOX: 8.24±1.87, PAZ: 9.67±4.66, TRAB: 6.97±3.23, TMZ: 4.28±1.41, respectively. TMZ significantly arrested the FDCS PDOX model compared to the control group (p<0.05). PAZ and TRAB did not have significant efficacy compared to the Ctrl group (p=0.93, p=0.41). In H&E-staining, partial necrosis was detected only in PDOX tumors treated with TMZ. There was no significant difference of body weight among all groups. Conclusion: The FDCS PDOX model was resistant to DOX as well as in the clinical settings demonstrating concordance of the FDCS model and clinic. TMZ was the most effective for the FDCS PDOX mouse model established from a patient who failed DOX treatment. There is possibility that TMZ has effective to FDCS patients who has resistant to the first line chemotherapy. Citation Format: Hiromichi Oshiro, Yasunori Tome, Robert M. Hoffman, Kotaro Nishida. Temozolomide suppresses a doxorubicin resistant follicular dendritic cell sarcoma in a patient derived orthotopic xenograft mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1661.

Combination of Trabectedin With Oxaliplatinum and 5-Fluorouracil Arrests a Primary Colorectal Cancer in a Patient-derived Orthotopic Xenograft Mouse Model.

In the present study, we aimed to determine the efficacy of trabectedin (TRAB) combined with oxaliplatinum (OXA)+5-fluorouracil (5-FU) on a colorectal cancer (CRC) patient-derived orthotopic xenograft (PDOX) mouse model. A patient CRC tumor previously established in nude mice was implanted subcutaneously in transgenic green fluorescence protein (GFP)-expressing nude mice. Harvested tumor fragments were transplanted orthotopically in non-transgenic nude mice. Mice were randomized into three groups: Group 1 (G1), untreated-control; Group 2 (G2), OXA+5-FU; Group 3 (G3), TRAB+OXA+5-FU. Tumor width, length, and mouse body weight were measured twice a week. Both treatment groups inhibited tumor growth compared to the untreated control group. The combination of TRAB, OXA and 5-FU was significantly more efficacious than OXA+5-FU and arrested tumor growth. No significant changes were observed in body-weight in any of the three groups. TRAB, OXA and 5-FU combination has clinical potential for this and other CRC patients.

Deciphering the transcriptional modulation program of trabectedin in sensitive and resistant patient derived xenograft models of myxoid liposarcoma

Deciphering the transcriptional modulation program of trabectedin in sensitive and resistant patient derived xenograft models of myxoid liposarcoma

The combination of gemcitabine and docetaxel arrests a doxorubicin-resistant dedifferentiated liposarcoma in a patient-derived orthotopic xenograft model

Liposarcoma (LS) is a chemotherapy-resistant disease. The aim of the present study was to find precise therapy for a recurrent dedifferentiated liposarcoma (DDLS) in a patient-derived orthotopic xenograft (PDOX) model. The DDLS PDOX models were established orthotopically in the right inguinal area of nude mice. The DDLS PDOX models were randomized into five groups: untreated; doxorubicin (DOX); gemcitabine (GEM) combined with docetaxel (DOC); pazopanib (PAZ); and yondelis (YON). On day 15, all mice were sacrificed. Measurement of tumor volume and body weight were done two times a week. The DDLS PDOX was resistant to DOX (P > 0.184). YON suppressed tumor growth significantly compared to control group (P < 0.027). However, only GEM combined with DOC arrested the tumor growth (P < 0.001). These findings suggest that GEM combined with DOC has clinical potential for this and possibly other DDLS patients.

A single-center retrospective study of patients treated with trabectedin (TRB) with long-term follow up.

11061 Background: TRB is FDA approved drug for the treatment of liposarcoma (Lipo) and leiomyosarcoma (LMS). The aim of this study was to evaluate potential biomarkers associated with prolonged benefit in patients treated with TRB at our center prior to 2016. Methods: We performed a retrospective search of UW/FHCRC CASIS database to identify patients treated with TRB prior to 2016. Demographic variables and clinical variables (such as histology and treatment) were retrieved. Statistics were performed with R 3.4.1 software. Pairwise Pearson’s correlation was calculated for the # of prior chemotherapy regimens with # of TRB cycles. The Kaplan-Meir method was used to evaluate overall survival (OS). Log-rank test was conducted to compare groups in terms of OS. Results: 145 sarcoma patients treated with TRB were identified with a mean follow up of 5 years (generally on NCT01427582 or NCT01343277). Patients averaged 1.9 prior chemotherapy regimens prior to TRB (range 0-7 regimens) and received an average of 5.6 TRB doses (range 1-25 doses). Subtypes are listed on table. The # of prior regimens was negatively correlated with the # of TRB cycles that patients received (pairwise correlation coefficient = -1.77; p=0.034), suggesting that multiple prior treatment lines either made TRB less tolerable or made sarcoma less sensitive to TRB. The median OS for this heavily treated metastatic population was 0.5 years. However, patients who were able to stay on TRB for more than 5 cycles had a significantly higher OS (p=0.001). While only 23% of patients who received less than 5 cycles of TRB were alive at 5 years (95% CI: 0.15, 0.32), 53% of those who received 5 or more cycles of (95% CI: 0.39, 0.65) were alive at 5 years. Conclusions: TRB may be more effective when administered as an earlier line of therapy. Patients who are able to stay on TRB for a longer duration had a significant improvement in OS. Detailed subset analysis will be presented as will initial findings of our biomarker work. These retrospective data warrant further evaluation. Clinical trial information: NCT01427582 or NCT01343277. [Table: see text]

Trabectedin and irinotecan combination regresses a cisplatinum-resistant osteosarcoma in a patient-derived orthotopic xenograft nude-mouse model

Recurrent osteosarcoma is a chemotherapy-resistant disease. Individualized precision therapy is needed for this disease. Toward this goal, we have developed the patient-derived othotopic xenograft (PDOX) mouse model of all major cancer types including osteosarcoma. Synergistic efficacy of trabectedin (TRAB) and irinotecan (IRT) has been reported in Ewing's sarcoma, soft-tissue sarcoma, and ovarian cancer. However, the efficacy of this combination on osteosarcoma is not known. The goal of present study was to determine the efficacy of the TRAB and IRT combination on cisplatinum (CDDP)-resistant osteosarcoma PDOX. The osteosarcoma PDOX models were randomized into five treatment groups of six mice: Untreated control; CDDP alone; TRAB alone; IRT alone; and TRAB and the IRT combination. Tumor size and body weight were measured during the 14 days of treatment. Tumor growth was regressed only by the TRAB-IRT combination. Tumors treated with the TRAB-IRT combination had the most tumor necrosis with degenerative change. The present study demonstrates the power of the PDOX model to identify a novel effective treatment strategy of the TRAB and IRT combination for chemotherapy-resistant osteosarcoma.

Temozolomide targets and arrests a doxorubicin-resistant follicular dendritic-cell sarcoma patient-derived orthotopic xenograft mouse model

Follicular dendritic cell sarcoma (FDCS) is a very rare and highly recalcitrant disease. A patient’s doxorubicin-resistant FDCS was previously established orthotopically on the right high thigh into the biceps femoris of mice to establish a patient-derived orthotopic xenograft (PDOX) model. The aim of the present manuscript was to identify an effective drug for this recalcitrant tumor. Here, we evaluated the efficacy of temozolomide (TMZ), trabectedin (TRAB) and pazopanib (PAZ) on the FDCS PDOX model. PDOX mouse models were randomized into five groups of eight to nine mice, respectively. Group 1, untreated control with PBS, i.p.; Group 2, treated with doxorubicin (DOX), 2.4 mg/kg, i.p., weekly for 3 weeks; Group 3, treated with PAZ, 50 mg/kg, oral gavage, daily for 3 weeks; Group 4, treated with TMZ, 25 mg/kg, oral gavage, daily for 3 weeks; Group 5, treated with TRAB, 0.15 mg/kg, i.v., weekly for 3 weeks. Body weight and tumor volume were assessed 2 times per week. TMZ arrested the FDCS PDOX model compared to the control group (p < 0.05). PAZ and TRAB did not have significant efficacy compared to the control group (p = 0.99, p = 0.69 respectively). The PDOX tumor was resistant to DOX (p= 0.99). as was the patient. The present study demonstrates that TMZ is effective for a PDOX model of FDCS established from a patient who failed DOX treatment, further demonstrating the power of PDOX to identify effective therapy including for tumors that failed first line therapy.

A patient-derived orthotopic xenograft (PDOX) nude-mouse model precisely identifies effective and ineffective therapies for recurrent leiomyosarcoma

Leiomyosarcoma is a rare and recalcitrant disease. Doxorubicin (DOX) is usually considered first-line treatment for this disease, but frequently is ineffective. In order to individualize therapy for this and other cancers, we have developed the patient-derived orthotopic xenograft (PDOX) mouse model. In the present study, we implanted a recurrent leiomyosarcoma from a resected tumor from the patient’s thigh into the femoral muscle of nude mice. The following drugs were tested on the leiomyosarcoma PDOX model: DOX, the combination of gemcitabine (GEM) and docetaxel (DOC), trabectedin (TRA), temozolomide (TEM), pazopanib (PAZ) and olaratumab (OLA). Of these agents GEM/DOC, TRA and TEM were highly effective in the leiomyosarcoma PDOX model, the other agents, including first-line therapy DOX, were ineffective. Thus the leiomyosarcoma PDOX model could precisely distinguish effective and ineffective drugs, demonstrating the potential of the PDOX model for leiomyosarcoma treatment.

Trabectedin arrests a doxorubicin-resistant PDGFRA-activated liposarcoma patient-derived orthotopic xenograft (PDOX) nude mouse model

BackgroundPleomorphic liposarcoma (PLPS) is a rare, heterogeneous and an aggressive variant of liposarcoma. Therefore, individualized therapy is urgently needed. Our recent reports suggest that trabectedin (TRAB) is effective against several patient-derived orthotopic xenograft (PDOX) mouse models. Here, we compared the efficacy of first-line therapy, doxorubicin (DOX), and TRAB in a platelet-derived growth factor receptor-α (PDGFRA)-amplified PLPS.MethodsWe used a fresh sample of PLPS tumor derived from a 68-year-old male patient diagnosed with a recurrent PLPS. Subcutaneous implantation of tumor tissue was performed in a nude mouse. After three weeks of implantation, tumor tissues were isolated and cut into small pieces. To match the patient a PDGFRA-amplified PLPS PDOX was created in the biceps femoris of nude mice. Mice were randomized into three groups: Group 1 (G1), control (untreated); Group 2 (G2), DOX-treated; Group 3 (G3), TRAB-treated. Measurement was done twice a week for tumor width, length, and mouse body weight.ResultsThe PLPS PDOX showed resistance towards DOX. However, TRAB could arrest the PLPS (p < 0.05 compared to control; p < 0.05 compared to DOX) without any significant changes in body-weight.ConclusionsThe data presented here suggest that for the individual patient the PLPS PDOX model could specifically distinguish both effective and ineffective drugs. This is especially crucial for PLPS because effective first-line therapy is harder to establish if it is not individualized.

A major response to trabectedin in metastatic malignant fibrous histiocytoma of the vertebra: a case report and review of the literature.

Malignant fibrous histiocytoma is an aggressive tumor, the most common soft-tissue sarcoma of adult age. It is usually located in the extremities and retroperitoneum, and very rarely there is skeletal involvement. Surgery is the preferred treatment in early disease; in advanced disease, chemotherapy is the main therapeutic strategy. We present a 25-year-old female patient diagnosed with a vertebral mass in T5 with a severely compromised spinal cord. She underwent surgical decompression and the pathological findings were consistent with malignant fibrous histiocytoma. After several surgical treatments she had pulmonary progression and was therefore started on chemotherapy. She had a very poor response to most of the administered regimens until she initiated trabectedin 1 mg/m 2 every three weeks. She showed a significant improvement with a major response of the lung metastases. This report indicates that trabectedin is an active drug in advanced, previously treated metastatic malignant fibrous histiocytoma.

Trabectedin-related rhabdomyolysis: an uncommon but fatal toxicity.

Rhabdomyolysis is defined as the dissolution of striped muscle characterized by the leakage of intracellular muscle components into the circulation, which can ultimately lead to renal failure with a possible fatal outcome. Trabectedin is a potential cause of rhabdomyolysis. Herein, we describe a case of rhabdomyolysis in a female patient with recurrent metastatic leiomyosarcoma of the uterus and who had full recovery, and we review the already published cases in order to identify a common pattern of emergence.

Problems in dealing with very rare adverse effects of new anticancer drugs: the example of trabectedin.

Problems in dealing with very rare adverse effects of new anticancer drugs: the example of trabectedin.

A patient-derived orthotopic xenograft (PDOX) mouse model of a cisplatinum-resistant osteosarcoma lung metastasis that was sensitive to temozolomide and trabectedin: implications for precision oncology.

In the present study, we evaluated the efficacy of trabectedin (TRAB) and temozolomide (TEM) compared to cisplatinum (CDDP) on a patient-derived orthotopic xenogrraft (PDOX) of a lung-metastasis from an osteosarcoma of a patient who failed CDDP therapy. Osteosarcoma resected from the patient was implanted orthotopically in the distal femur of mice to establish PDOX models which were randomized into the following groups when tumor volume reached approximately 100 mm3: G1, control without treatment; G2, CDDP (6 mg/kg, intraperitoneal injection, weekly, for 2 weeks); G3, TRAB (0.15 mg/kg, intravenous injection, weekly, for 2 weeks); G4, TEM (25 mg/kg, oral, daily, for 14 days). Tumor size and body weight were measured with calipers and a digital balance, respectively, twice a week. On day 14 after initiation of treatment, TEM and TRAB, but not CDDP, significantly inhibited tumor volume compared to untreated control: control (G1): 814.5±258.8 mm3; CDDP (G2): 608.6±126.9 mm3; TRAB (G3): 286.6±133.0 mm3; TEM (G4): 182.9±69.1 mm3. CDDP vs. control, p=0.07; TRAB vs. control, p=0.0004; TEM vs. control p =0.0002; TRAB vs. CDDP, p =0.0002; TEM vs. CDDP, p =0.00003. The results of the present study show that a PDOX model of an osteosarcoma lung-metastasis that recurred after adjuvant CDDP-treatment has identified potentially, highly-effective drugs for this recalcitrant disease, while accurately maintaining the CDDP resistance of the tumor in the patient, thereby demonstrating the potential of the osteosarcoma PDOX model for precision oncology.

Antitumor activity of trabectedin and lurbinectedin in germline BRCA2 carriers with metastatic breast cancer (MBC) as compared to BRCA1 carriers: Analysis of two phase II trials.

574 Background: BRCA 1/2-associated breast cancer share homologous recombination deficiency, but also have independent and potentially actionable roles. Novel drugs with innovative mechanism of action, lacking cross-resistance with other used agents are needed for BRCA 1/2 MBC. Trabectedin (TR) and its analog, lurbinectedin (L), have shown to be active in BRCA 1/2 MBC. This study was sought to determine if there was a difference in activity of these agents between BRCA1 and 2 carriers. Methods: Safety and efficacy in MBC BRCA 1/2 were analyzed in 2 separate phase II trials of single agent TR and L. Results: 88 patients were evaluated: 34 with TR, 54 with L. Median age: 46 and 43, respectively. Median (range) prior chemotherapy lines: TR, 4 (1-10); L, 2 (0-5). Clinical responses were seen in the 2 trials (see table) and were higher in BRCA2 than in BRCA1 (33% vs 9% with TR and 61% vs 26% with L). Main adverse event was myelosuppression (grade 3-4 neutropenia / thrombocytopenia / febrile neutropenia: TR, 62.1%/24.3%/10.8% L, 66.7%/20.4%/20.4%). Non-hematological toxicity was mostly grade 1-2: fatigue, nausea/vomiting and high transaminases (grade 3/4 TR, 40.5%, L 18.5%). Conclusions: Remarkable activity of trabectedin and lurbinectedin as single agents was observed in BRCA 2 associated MBC. This finding warrants further investigation. One potential mechanistic rationale is the role of both lurbinectedin and BRCA 2 in transcription. Safety was acceptable and manageable in both studies. Clinical trial information: NCT01525589. [Table: see text]