Objective:To investigate the efficacy and safety of radium-223 in combination with new-generation hormonal agents in patients with bone metastases of prostate cancer.Methods:The clinical data of 17 patients (12 from the First Affiliated Hospital of Airforce Military Medical University and 5 from Xi'an International Medical Center Hospital) with metastatic castration-resistant prostate cancer(mCRPC) treated by radium-223 combined with new-generation hormonal agents from January 2021 to June 2022 were retrospectively analyzed. In all cases, the average age was (73.3±8.5) years old. Before treatment, the median prostate-specific antigen (PSA) was 15.7 (3.2, 36.5) ng/ml, the median alkaline phosphatase (ALP) was 131.5 (79.0, 430.7) U/L. All patients had ≥ 2 bone metastases but no visceral or lymph node metastases. The median number of bone scan lesions was 10(8, 15). Bone pain symptom was present in 16(94.1%) patients. There were 9 cases (52.9%) with Eastern Cooperative Oncology Group (ECOG) score of ≥2, 1 case (5.9%) with ECOG score of 1 and 6 cases (35.2%) with ECOG score of 0. All patients were treated with radium-223 (55 kBq/kg, injected every 4 weeks for a maximum of 6 cycles), of which 5 patients were combined with enzalutamide, 8 patients combined with apatamide and 4 patients combined with bicalutamide. PSA response (PSA decreased by ≥30% from baseline and maintained for at least 1 month), ALP response (ALP decreased by ≥30% from baseline and maintained for at least 1 month) and pain relief rates were analyzed. Imaging evaluation was performed before and after treatment to calculate the objective response rate of metastases. The incidence of treatment-related adverse effects and skeletal related event (SRE) were also recorded.Results:Eleven patients completed 6 courses, 3 patients completed 5 courses and 3 patients completed ≥4 courses. The median ALP after 1 month of last treatment was 83.2 (51.5, 126.5) U/L, which was significantly decreased than baseline. 12 patients (70.6%) showed an ALP response and the other 5 (29.4%) showed varying degrees of ALP elevation. PSA response was observed in 4 patients (23.5%), of which 2 (11.8%) had a continuous decrease and 2 (11.8%) had a late-stage increase in PSA. Pain relief was relieved in 15 cases (88.2%) during treatment, 1 case (5.9%) had worsening pain due to disease progression and 1 case (5.9%) had no change during treatment. The ECOG score decreased in 15 (88.2%) patients. The median number of bone metastases in patients decreased to 5 (4, 9). One patient (5.9%) had complete remission during treatment, 11 patients (64.7%) had a partial response, 4 patients (23.5%) were stable, and 1 (5.9%) showed imaging progression after 4 months of treatment. The overall objective remission response rate was 70.5% (12/17). Treatment-related hematologic adverse effects included anemia (1 case, 5.9%, grade 3), thrombocytopenia (1 case, 5.9%, grade 3) and leukopenia (1 case, 5.9%, grade 2). Non-hematologic adverse effects included fatigue (3 cases, 17.6%, 2 cases in grade 1, 1 case in grade 2), gastrointestinal bleeding (1 case, 5.9%, grade 3), diarrhea (1 case, 5.9%, grade 2) and fever (1 case, 5.9%, grade 1). Patients with grades 1 to 2 relieved with symptomatic management. Three cases (17.6%) were discontinued due to intolerance of grade 3 adverse reactions and 1 case (5.9%) terminated on its own. There was no SRE during treatment and follow-up.Conclusions:Radium-223 combined with New-generation hormonal agents has a high objective remission rate in patients with mCRPC, which could provide pain relief and improve quality of life. The incidence of adverse reactions was low and well tolerated.

Polymyxin B and polymyxin E (colistin) are presently considered the last line of defense against human infections caused by multidrug-resistant Gram-negative organisms such as carbapenemase-producer Enterobacterales, Acinetobacter baumannii, and Klebsiella pneumoniae. Yet resistance to this last-line drugs is a major public health threat and is rapidly increasing. Polymyxin S₂ (S₂) is a polymyxin B analogue previously synthesized in our institute with obviously high antibacterial activity and lower toxicity than polymyxin B and colistin. To predict the possible resistant mechanism of S₂ for wide clinical application, we experimentally induced bacterial resistant mutants and studied the preliminary resistance mechanisms. Mut-S, a resistant mutant of K. pneumoniae ATCC BAA-2146 (Kpn2146) induced by S₂, was analyzed by whole genome sequencing, transcriptomics, mass spectrometry and complementation experiment. Surprisingly, large-scale genomic inversion (LSGI) of approximately 1.1 Mbp in the chromosome caused by IS26 mediated intramolecular transposition was found in Mut-S, which led to mgrB truncation, lipid A modification and hence S₂ resistance. The resistance can be complemented by plasmid carrying intact mgrB. The same mechanism was also found in polymyxin B and colistin induced drug-resistant mutants of Kpn2146 (Mut-B and Mut-E, respectively). This is the first report of polymyxin resistance caused by IS26 intramolecular transposition mediated mgrB truncation in chromosome in K. pneumoniae. The findings broaden our scope of knowledge for polymyxin resistance and enriched our understanding of how bacteria can manage to survive in the presence of antibiotics.