Fierce-21: Phase II study of vofatmab (B-701), a selective inhibitor of FGFR3, as salvage therapy in metastatic urothelial carcinoma (mUC)

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Background: Patients (pts) with mUC who have failed platinum-based chemotherapy have a poor prognosis. About 20% of them usually respond to immune checkpoint inhibitors (ICI). Also, 20% of pts with mUC harbor FGFR3 mutations or fusions (M/F), and this feature may be associated with lower sensitivity to ICI. Vofatamab (B-701) is a fully human monoclonal antibody against FGFR3 that blocks activation of the wildtype and genetically activated receptor. FIERCE-21 is a Phase 1b/2 study designed to evaluate vofatamab monotherapy (VM) or in combination with docetaxel (VD). Methods: The study consists of a P 1b lead-in (P1b with VD), previously reported followed by P2 expansion cohort in FGFR3 M/F+ pts (identified with the FoundationONE CDx™ assay on archival samples). The study enrolled mUC pts with failure to ≥ 1 line prior chemotherapy (including prior taxane treatment) or ≤12 months of (neo)adjuvant chemotherapy, measurable disease and ECOG ≤ 1. Treatment consisted of vofatamab at 25 mg/kg alone (VM) and in combination with D (VD) at 75 mg/m2 q3w. Efficacy was assessed by investigators (RECIST 1.1). Primary objectives were safety and activity (objective response-rate [ORR]). Results: 55 pts have received treatment. In the Ph 2 study, 21 pts received VM, 15 pts received VD. 35% of pts were included as 2nd line therapy, 65% in 3rd or later line of treatment. For pts receiving VD, safety was consistent with Ph 1B data. For pts receiving VM, median age was 67 yrs, ECOG 1 = 71.4%, Hgb < 10 gm/dL 13%, liver metastases 19%, ≥ 2 prior regimens 57%, (best response to prior therapy PD 31%). TEAEs occurring in ≥5% patients were asthenia (19%), diarrhea (9.5%), flushing 14%, chills (9.5%), hypotension (9.5%), decreased appetite (19%) and creatinine increased (9.5%). The majority of TEAS were grade 1 and 2. Only 1 patient on MF had a grade 3 TEAE and only 1 patient discontinued treatment due to an AE. The ORR have been seen in 7 pts to date including those receiving both VM and VD. Conclusions: Vofatamab both alone and combined with D in an every 3-week schedule are well tolerated with a low frequency of grade 3 TEAEs. Both VM and VD have demonstrated efficacy in terms of ORR, and mature results with PFS data will be presented. Clinical trial information: NCT02401542.

Results of a phase II trial of efficacy and safety of entospletinib (ENTO) in patients with lymphoplasmacytoid lymphoma/Waldenstrom's macroglubulinemia (LPL/WM)

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Background: ENTO is an orally bioavailable, selective inhibitor of spleen tyrosine kinase (Syk, a mediator of B-cell receptor [BCR] signaling). Targeting the BCR-signaling pathway has been a focus in B-cell related hematological malignancies including LPL/WM. Methods: This reports the LPL cohort in a phase 2 trial that more broadly evaluated efficacy and safety of ENTO (800 mg BID) in patients with relapsed and refractory (R/R) B-cell malignancies. Tumor response was assessed at weeks 8, 16, 24, and then every 12 weeks. The primary endpoint was PFS at week 24. Results: 17 LPL patients (median age 72 years [range: 47–89], 65% male, and median of 3 prior regimens [range: 1–8]) were enrolled. Prior therapies included anti-CD20 antibodies (100%), alkylating agents (71%; bendamustine 24%), purine analogues (24%), and vinca alkaloid (41%). No patient had prior ibrutinib. Median treatment duration was 16 weeks (range: 1-84), with 3 patients continuing on treatment. The most common treatment-emergent AEs (any grade/≥grade 3, independent of causality) were fatigue (53%, 6%), constipation (47%, 0%), nausea (47%, 6%), diarrhea (29%, 6%), insomnia (29%, 0%) and lab abnormalities including neutropenia (53%, 12%), increased creatinine (53%, 0%), increased ALT (41%, 6%) and decreased WBC (41%, 6%). One death due to progressive disease (PD) was reported within 30 days from last dose. 12 (71%) patients were evaluable for tumor response. 5 patients (29%) discontinued prior to initial tumor assessment: PD (n = 2), withdrawal consent (n = 2) and AE (n = 1). ORR was 24% (90% CI: 9%, 46%), with 1 (6%) patient achieving PR, 3 with minor response (18%) and 7 (41%) maintaining stable disease. Reductions of IgM from baseline were greatest in the patient with PR. PFS rate at week 24 was 82% (95% CI: 44%, 95%). Median time to treatment failure and median time to response were 3.7m and 1.9 m respectively. Median duration of response has not been reached. Conclusions: ENTO was well tolerated and demonstrated limited activity in patients with R/R LPL. Further development of ENTO in LPL will focus on its role in combination therapies. Clinical trial information: NCT01799889.