Emerging Therapies in Penile Cancer

Advances in the treatment of rare tumors like penile cancer were always hampered by the lack of deep comprehension of the molecular biology and genomic and epigenomic alterations involved in carcinogenesis and tumor progression, as well as by the difficulty in recruitment of patients for prospective clinical trials. Despite the high rates of cure in early localized penile cancers with surgery or other local procedures, locally advanced and metastatic tumors require systemic treatment, with chemotherapy being the current standard, but with high toxicity and no proven real impact on survival. Recent important findings of frequent genomic alterations and mutation signatures in penile cancer have motivated several trials in new modalities of systemic treatments, especially immunotherapy. This review aims to present the most recent advances and the prospect of new modalities of systemic therapies with ongoing studies in penile cancer.

Measuring Tumor Epichaperome Expression Using [124I] PU-H71 Positron Emission Tomography as a Biomarker of Response for PU-H71 Plus Nab-Paclitaxel in HER2-Negative Metastatic Breast Cancer

PURPOSE

Epichaperome network maintenance is vital to survival of tumors that express it. PU-H71 is an epichaperome inhibitor that binds to the ATP-binding site of HSP90 and has demonstrated antitumor activity in breast cancer xenograft models and clinical safety in patients. PU-positron emission tomography (PET) is a theragnostic imaging tool that allows visualization of the epichaperome target. In this phase Ib trial, we present safety and tolerability for PU-H71 plus nab-paclitaxel in HER2-negative patients with metastatic breast cancer (MBC) and the utility of PU-PET as a noninvasive predictive biomarker.

METHODS

We performed a 3 + 3 dose-escalation study with escalating PU-H71 doses and standard nab-paclitaxel. The primary objective was to establish safety and determine maximum tolerated dose (MTD)/recommended phase 2 dose. Secondary objectives were to assess pharmacokinetics and clinical efficacy. Patients could enroll in a companion PU-PET protocol to measure epichaperome expression before treatment initiation to allow exploratory correlation with treatment benefit.

RESULTS

Of the 12 patients enrolled, dose-limiting toxicity occurred in one patient (G3 neutropenic fever) at dose level 1; MTD of PU-H71 was 300 mg/m² plus nab-paclitaxel 260 mg/m² administered every 3 weeks. Common toxicities included diarrhea, fatigue, peripheral neuropathy, and nausea. PU-H71 systemic exposure was not altered by nab-paclitaxel administration. Two of 12 patients had partial response (overall response rate, 17%) and the clinical benefit rate was 42% (5 of 12). Time to progression was associated with baseline epichaperome positivity and PU-H71 peak standard uptake value (SUV), with more durable disease control observed with high epichaperome levels.

CONCLUSION

The combination of PU-H71 and nab-paclitaxel was well tolerated, with evidence of clinical activity. More durable disease control without progression was observed in patients with high baseline epichaperome expression. A phase II trial of this combination with PU-PET as a companion diagnostic for patient selection is currently planned.

A phase I trial of ganetespib in combination with paclitaxel and trastuzumab in patients with human epidermal growth factor receptor-2 (HER2)-positive metastatic breast cancer

BACKGROUND

Targeted therapies in HER2-positive metastatic breast cancer significantly improve outcomes but efficacy is limited by therapeutic resistance. HER2 is an acutely sensitive Heat Shock Protein 90 (HSP90) client and HSP90 inhibition can overcome trastuzumab resistance. Preclinical data suggest that HSP90 inhibition is synergistic with taxanes with the potential for significant clinical activity. We therefore tested ganetespib, a HSP90 inhibitor, in combination with paclitaxel and trastuzumab in patients with trastuzumab-refractory HER2-positive metastatic breast cancer.

METHODS

In this phase I dose-escalation study, patients with trastuzumab-resistant HER2-positive metastatic breast cancer received weekly trastuzumab (2 mg/kg) and paclitaxel (80 mg/m²) on days 1, 8, 15, and 22 of a 28-day cycle with escalating doses of ganetespib (100 mg/m², 150 mg/m², and a third cohort of 125 mg/m² if needed) on days 1, 8, and 15. Therapy was continued until disease progression or toxicity. The primary objective was to establish the safety and maximum tolerated dose and/or recommended phase II dose (RP2D) of this therapy. The secondary objectives included evaluation of the effects of ganetespib on the pharmacokinetics of paclitaxel, and to make a preliminary assessment of the efficacy of the combination therapy.

RESULTS

Dose escalation was completed for the two main cohorts without any observed dose-limiting toxicities. Nine patients received treatment. The median prior lines of anti-HER2 therapy numbered three (range 2-4), including prior pertuzumab in 9/9 patients and ado-trastuzumab emtansine (T-DM1) in 8/9 patients. The most common grade 1/2 adverse events (AEs) were diarrhea, fatigue, anemia, and rash. There were no grade 4 AEs related to ganetespib. The overall response rate was 22% (2/9 patients had partial response) and stable disease was seen in 56% (5/9 patients). The clinical benefit rate was 44% (4/9 patients). The median progression-free survival was 20 weeks (range 8-55).

CONCLUSION

The RP2D of ganetespib is 150 mg/m² in combination with weekly paclitaxel plus trastuzumab. The combination was safe and well tolerated. Despite prior taxanes, pertuzumab, and T-DM1, clinical activity of this triplet regimen in this heavily pretreated cohort is promising and warrants further study in HER2-positive metastatic breast cancer.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02060253 . Registered 30 January 2014.

HSP90 stabilizes B-cell receptor kinases in a multi-client interactome: PU-H71 induces CLL apoptosis in a cytoprotective microenvironment

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of B cells in the hematopoietic system and lymphoid tissues. Although inhibitors targeting the B-cell receptor (BCR) pathway have been successful in the treatment of the disease, the underlying mechanisms leading to BCR over-activity in CLL are not fully understood. In this study, we found that HSP90, a highly conserved molecular chaperone, is overexpressed in CLL compared with resting B cells. HSP90 overexpression is accompanied by the overexpression of several BCR kinases including LYN, spleen tyrosine kinase, Bruton tyrosine kinase and AKT. Chemical and immune-precipitation demonstrated that these BCR constituents are present in a multi-client chaperone complex with HSP90. Inhibition of HSP90 with PU-H71 destabilized the BCR kinases and caused apoptosis of CLL cells through the mitochondrial apoptotic pathway. Further, PU-H71 induced apoptosis in the presence of stromal co-culture or cytoprotective survival signals. Finally, genetic knockdown of HSP90 and its client AKT, but not BTK, reduced CLL viability. Overall, our study suggests that the chaperone function of HSP90 contributes to the over-activity of the BCR signaling in CLL and inhibition of HSP90 has the potential to achieve a multi-targeting effect. Thus, HSP90 inhibition may be explored to prevent or overcome drug resistance to single targeting agents.