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4108 Background: PPGL, rare neuroendocrine tumors with a 5-yr survival rate as low as 12%, have a high unmet need for effective treatment options. AZEDRA, a high-specific-activity iodine-131 meta-iodobenzylguanidine (HSA I-131-MIBG), is the first and only FDA- approved therapeutic radiopharmaceutical agent indicated for the treatment of adult and pediatric pts with iobenguane scan positive, unresectable, locally advanced or metastatic PPGL who require systemic anticancer therapy. Methods: Pts with advanced disease who were heavily pre-treated and were ineligible for curative surgery or chemotherapy received a dosimetric dose followed by up to two therapeutic doses (each at 296 MBq/kg to a max of 18.5 GBq). The primary endpoint, defined as the proportion of pts with at least 50% reduction of all antihypertensive medication(s) lasting ≥6 months, was met and previously reported. Updated secondary endpoints including overall survival (OS) and safety are reported. Results: A dosimetric dose of HSA I-131-MIBG was administered to 74 pts. Of those, 68 pts received one therapeutic dose and 50 received two doses of HSA I-131-MIBG. Clinical benefit rates (objective tumor responses defined by RECIST 1.0 and stable disease) were observed in 71.4% and 98.0% of pts receiving one and two therapeutic doses, respectively. As of Jan 25, 2019, median OS for all pts was 41.1 months (95% CI 31.1, 91.2). Median OS was 17.5 months (95% CI 4.0, 31.5) and 48.7 months (95% CI 33.2, 91.2) in pts receiving one and two doses, respectively. A tail of survival was observed, with OS of 73.1% at 2 yrs and 44.2% at 4 yrs. The most common (≥50%) adverse events were nausea, fatigue, and myelosuppression. Myelosuppressive events resolved within 4-8 wks without requiring stem cell transplantation. Late radiation toxicity included 8 pts with secondary malignancies (myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), colon cancer, and lung carcinoma) of which MDS, ALL and AML were considered related to I-131 radiotherapy. Conclusions: Updated results from this pivotal phase 2 study suggest that HSA I-131-MIBG is an efficacious and safe treatment for advanced PPGL. Clinical trial information: NCT00874614.

4005Background: AZEDRA, a high-specific-activity iodine-131 meta-iodobenzylguanidine (HSA I-131 MIBG), has been developed for the treatment of iobenguane-avid malignant (metastatic) or recurrent or...

395 Background: Telotristat ethyl (TE) is approved to treat inadequately controlled carcinoid syndrome (CS) diarrhea in combination with somatostatin analog (SSA) therapy. Understanding the time to onset of sustained BM frequency improvement is important when considering the use of TE in patients with CS diarrhea. We present data on time to sustained improvement and worsening in BM frequency during the double-blind treatment (DBT) period of TELECAST, a phase 3, randomized, placebo-controlled, double-blind study in patients with CS that required additional treatment, primarily due to gastrointestinal symptoms. Methods: Stable dose SSA was not required. Patients were treated with TE 250 mg 3 times per day (tid), TE 500 mg tid, or placebo tid. Sustained response was defined as the time from the first double-blind dose date to the first day of 2 consecutive weeks with BM frequency change of at least 30% from baseline. The time to the first sustained response in the TELECAST study was examined among treatment groups and analyzed using Cox regression. Results: There were 26 patients on placebo and 25 patients on either 250 mg or 500 mg telotristat groups. Sustained improvement in BM frequency over the 12-week DBT period was achieved in 6, 16, and 16 patients on placebo, TE 250 mg, and TE 500 mg treatment groups. Median time to sustained ≥ 30% improvement was 4-5 weeks with TE at both dosing levels, with no median reached on placebo. First occurrence of sustained improvements in BM frequency occurred within 4-68 days. Time to sustained worsening was delayed on the 500-mg dose of TE (no percentile reached) and is statistically significant (p = 0.021, HR: 0.25) Conclusions: Treatment with telotristat ethyl may provide sustained BM frequency reduction within 4-5 weeks (median) of initiating therapy. No median was reached on placebo due to fewer patients with sustained improvement. Additionally, TE 500 mg tid may also offer additional clinical benefit by reducing sustained BM worsening. Clinical trial information: NCT02063659.