From the Journals

PSMA-targeting docetaxel nanoparticles active, safe for mCRPC


Key clinical point: A docetaxel-encapsulating nanoparticle targeted against PSMA was safe and showed good activity.

Major finding: The 6-month PFS rate, the primary endpoint, was 65%.

Study details: Open label phase 2 trial of 42 men with mCRPC that progressed on abiraterone acetate and/or enzalutamide.

Disclosures: The study was funded by BIND Therapeutics and by grants from the National Institutes of Health, Sidney Kimmel Center for Prostate and Urologic Cancers, and the David H. Koch Prostate Cancer Research Fund. Dr. Autio had no disclosures. Several coauthors are employees of BIND Therapeutics, and others are employed by Epic Sciences, maker of the CTC assay used in the study. Other coauthors reported advising/consulting, research support, and speakers bureau activities for multiple companies.

Source: Autio KA et al. JAMA Oncol. 2018 July 5. doi: 10.1001/jamaoncol.2018.2168.



For men with chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC), a docetaxel-containing nanoparticle directed against prostate-specific membrane antigen (PSMA) was both active and well tolerated.

Among 42 men with mCRPC that had progressed after treatment with abiraterone acetate (Zytiga) and/or enzalutamide (Xtandi), the 6-month radiographic progression-free survival (PFS) rate, the primary endpoint, was 65%, and approximately one-third of evaluable patients had a prostate-specific antigen (PSA) response and measurable disease response, reported Karen A. Autio, MD, MSc, of Memorial Sloan Kettering Cancer Center, New York, and her colleagues.

Treatment with the PSMA-directed docetaxel-containing nanoparticle, called BIND-014, was also associated in some patients with a rapid and robust decline in PSMA-positive circulating tumor cells (CTCs), the investigators noted. The report was published in JAMA Oncology.

“Many aspects of our study – reductions in PSA, radiographically confirmed disease control in bone and visceral metastatic disease, favorable CTC conversions, and an acceptable adverse effect profile – were promising for BIND-014. However, standard therapy with docetaxel is widely used and effective in treating this disease, and as a natural comparator for a phase 3 randomized clinical trial with BIND-014, it sets a high bar for efficacy in an unselected population,” they wrote.

Their findings suggest that patients with PSMA-positive CTCs might be good candidates for treatment with BIND-014, which is associated with lower toxicities than standard docetaxel, the investigators said.

In the open-label phase 2 trial, 42 men (median age 66) with chemotherapy-naive mCRPC that had progressed on abiraterone and/or enzalutamide were treated with intravenous BIND-014 at dosages of 60 mg/m2 on the first day of each 21-day cycle, plus prednisone 5 mg twice daily, until disease progression, intolerable toxicity, or treatment discontinuation at the treating physician’s discretion.

The median number of doses delivered was six.

Of 40 evaluable patients, 12 (30%) had a PSA response, defined as a decrease of 50% or greater from baseline. Among 19 patients with disease measurable according to Response Evaluation Criteria in Solid Tumors, version 1.1, six (32%) had responses, including one complete response and five partial responses. Nine other patients had stable disease.

The median PFS was 9.9 months. As noted, the radiographic PFS rate at 6 months was 65% (26 of 40 patients).

CTC enumeration was performed on samples from 39 patients, of whom 67% had unfavorable counts at baseline, defined as 5 or more CTCs per 7.5 mL of blood.

After treatment, 13 of the patients had a conversion to a favorable count, including 6 whose CTCs became undetectable.

The most common treatment-related adverse events were fatigue, occurring in 69% of patients, nausea in 55%, diarrhea in 45%, and patient-reported neuropathy in 33%. Most toxicities were grade 1 or 2.

Grade 3 or 4 hematological toxicities included lymphopenia in five patients, anemia in three, neutropenia in one, leukopenia in one, and febrile neutropenia in one.

Nonhematological grade 3 or 4 events included fatigue and nausea in two patients each, and dyspnea and decreased appetite in one patient each.

“In this trial, two principal lessons are worth highlighting: the reduction in both total CTCs, which is a marker of clinical benefit, and specifically PSMA-positive CTCs, suggests that the detection of PSMA-positive CTCs before treatment can be used to identify patients who are most likely to benefit in addition to serving as a pharmacodynamic measure,” the investigators wrote.

“Second, there was marked intrapatient and interpatient heterogeneity of PSMA expression on CTCs. This underscores the complexity of targeting tumors with single cell-surface markers,” they wrote.

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