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Recent trials have shown the efficacy of trastuzumab deruxtecan (T-DXd) in HER2-negative patients, but there is not yet a way to identify which patients will best respond, especially with the inability of current HER2 IHC and FISH assays to accurately determine HER2 expression in the unamplified setting. Here, we present a heavily pre-treated patient with triple-negative breast cancer (HER2 IHC 0 who had a complete response to T-DXd. In this case, we used a CLIA-certified reverse-phase protein array-based proteomic assay (RPPA) to determine that the patient had moderate HER2 protein expression (HER2Total 2+, 42%) and activation (HER2Y1248 1+, 23%). Using these results, we determined that the patient may benefit from T-Dxd despite being traditionally qualified as HER2 IHC 0. These findings highlight the potential for proteomics-based assays that may more accurately quantitate HER2 and (its activation) in the HER2 unamplified/IHC 0 setting to better select patients whose tumors are classically molecularly defined as HER2 IHC 0, but still could respond to HER2-directed therapy, and give patients access to therapies which for which they otherwise would not be eligible. [ABSTRACT FROM AUTHOR]

Purpose: This phase II study evaluated the efficacy and tolerability of onvansertib, a polo-like kinase 1 (PLK1) inhibitor, in combination with fluorouracil, leucovorin, and irinotecan (FOLFIRI) + bevacizumab for the second-line treatment of KRAS -mutant metastatic colorectal cancer (mCRC)., Patients and Methods: This multicenter, open-label, single-arm study enrolled patients with KRAS -mutated mCRC previously treated with oxaliplatin and fluorouracil with or without bevacizumab. Patients received onvansertib (15 mg/m 2 once daily on days 1-5 and 15-19 of a 28-day cycle) and FOLFIRI + bevacizumab (days 1 and 15). The primary end point was the objective response rate (ORR), and secondary endpoints included progression-free survival (PFS), duration of response (DOR), and tolerability. Translational and preclinical studies were conducted in KRAS -mutant CRC., Results: Among the 53 patients treated, the confirmed ORR was 26.4% (95% CI, 15.3 to 40.3). The median DOR was 11.7 months (95% CI, 9.4 to not reached). Grade 3/4 adverse events were reported in 62% of patients. A post hoc analysis revealed that patients with no prior bevacizumab treatment had a significantly higher ORR and longer PFS compared with patients with prior bevacizumab treatment: ORR of 76.9% versus 10.0% (odds ratio of 30.0, P < .001) and median PFS of 14.9 months versus 6.6 months (hazard ratio of 0.16, P < .001). Our translational findings support that prior bevacizumab exposure contributes to onvansertib resistance. Preclinically, we showed that onvansertib inhibited the hypoxia pathway and exhibited robust antitumor activity in combination with bevacizumab through the inhibition of angiogenesis., Conclusion: Onvansertib in combination with FOLFIRI + bevacizumab showed significant activity in the second-line treatment of patients with KRAS -mutant mCRC, particularly in patients with no prior bevacizumab treatment. These findings led to the evaluation of the combination in the first-line setting (ClinicalTrails.gov identifier: NCT06106308).

Purpose: Targeted Agent and Profiling Utilization Registry is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer and targetable genomic alterations. Two cohorts of patients with cyclin-dependent kinase inhibitor 2A ( CDKN2A )-mutated tumors treated with palbociclib are reported: one with head and neck cancer (HNC) with both squamous and nonsquamous cell histologies, and one with histology-pooled (HP) cancers., Methods: Eligible patients had measurable disease, Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, and no standard treatment options. The primary end point was disease control (DC), defined as objective response (OR) or stable disease (SD) of at least 16+ weeks duration. For the HNC cohort, Simon's two-stage design with a null DC rate of 15% versus 35% (power = 0.85; α = .10) was used. For the HP cohort, the null hypothesis of a DC rate of 15% was rejected if the lower limit of a one-sided 90% CI was >15%. Secondary end points included OR, safety, progression-free survival, overall survival, duration of response, and duration of SD., Results: Seventy patients with HNC (N = 28) or HP cancers (N = 42) were treated with palbociclib. For the HNC cohort, DC and OR rates were 40% (one-sided 90% CI, 27 to 100) and 4% (95% CI, <1 to 18), respectively. The null hypothesis was rejected ( P = .002). For the HP cohort, DC and OR rates were 13% (one-sided 90% CI, 6 to 100) and 5% (95% CI, <1 to 17), respectively. The null hypothesis was not rejected. Thirty-one of 70 patients experienced treatment-related grade 3 to 4 adverse events (AEs) or serious AEs, the most common including neutropenia, thrombocytopenia, and leukopenia., Conclusion: Palbociclib met prespecified criteria to declare a signal of activity in patients with HNC with CDKN2A alterations, but not in the HP cohort.