Telotristat

Limits on what this shows

• Null findings: No mitochondrial damage marker, membrane potential, respiration assay or ATP content was reported in [25] (ATP and ROS not measured). The Ling 2024 abstract [19] reports elevated succinic acid in colon, which is not a mitochondrial function measurement.
• At-risk subgroups: Not defined; adipose browning in mice is not shown in patients, and telotristat reduces peripheral serotonin in humans without any retrieved mitochondrial or thermogenic outcome.

Regulatory status

No mitochondrial statement in the label text [1][2]; EU public assessment report search found none [27].

Population evidence

Cohort test: telotristat NOT in cohort. Oh et al. 2015 [25], mice: PCPA 300 mg/kg intraperitoneal daily for 12 weeks (n=4 per group): "the number and size of the mitochondria and the density of the cristae were increased in the BAT of PCPA-treated mice"; higher oxygen consumption and heat production on a high-fat diet; reduced weight gain. LP-533401 (the peripheral inhibitor, 30 mg/kg oral gavage daily for 14 weeks, n=5 per group) reduced weight gain and improved glucose tolerance; the mitochondrial and oxygen consumption statements were attributed to PCPA, not LP-533401, in the text retrieved. Inducible adipocyte Tph1 knockout mice (n=4 per group) showed reduced weight gain and improved glucose and insulin handling. The telotristat in vitro study [10] (BON-1 and QGP-1 pancreatic NET cells) found MTT metabolic activity unchanged.

Mechanism

Present in rodents (Tier C): reduced serotonin signaling through Htr3 increased thermogenic activity of brown fat, with Ucp1 and Dio2 expression increased in white fat [25]. It is a metabolic-rate and thermogenesis finding, not a mitochondrial toxicity finding.

Counter-evidence held on record

Counter-evidence and confounding PCPA is not telotristat and the paper describes LP-533401, not PCPA, as the peripheral inhibitor; the mitochondrial finding comes from PCPA with n=4 per group. Direction is favorable or neutral (greater mitochondrial mass), so this entry gives no basis for a depletion or injury claim. Framing caution A reverse-direction research flag from rodent adipose tissue. It does not describe mitochondrial harm or benefit in patients taking telotristat; no supplement is implied.

Limits on what this shows

• Null findings: The telotristat in vitro study [10] did not measure ROS or oxidative markers. The LP-533401 and PCPA energy-homeostasis study [25] reported no oxidative stress or ROS measurements. No glutathione, MDA, SOD or 8-isoprostane data for any TPH inhibitor were found.
• At-risk subgroups: Not defined.

Regulatory status

No oxidative stress statement in the label text [1][2]; EU public assessment report search found none [27].

Population evidence

Cohort test: telotristat NOT in cohort. Ling et al. 2024 [19]: LP533401 in neonatal rats (day 4 to day 11); "decreased ascorbate and elevated succinic acid correlating with serotonin levels and crypt depth" in untargeted metabolomics of the colonic microenvironment (abstract only; tissue or sample type, magnitude, n and statistics were not captured; full text not opened). Ascorbate is an antioxidant metabolite and succinate accumulation is linked in the wider literature to mitochondrial redox state, but neither was validated here as a redox-capacity marker.

Mechanism

Unclear. The abstract links the metabolite changes to serotonin levels and crypt depth, not to a redox mechanism. This is a hypothesis-generating metabolite shift in neonatal rat colon, not a systemic oxidative stress measurement.

Counter-evidence held on record

Counter-evidence and confounding Single untargeted metabolite shift from one abstract; it does not satisfy Hard Rule 3 as a validated functional marker, so it is not an oxidative stress or vitamin C status claim. Neonatal age, colonic tissue and a different compound limit transfer to adult telotristat users. Framing caution Not a vitamin C deficiency claim and not evidence of oxidative damage from telotristat. No antioxidant supplementation is implied; no dose appears in this dossier.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence for telotristat or another TPH inhibitor and copper, and no circulating copper claim found. Kept independent of Iron (Hard Rule 7). Re-check when PubMed access is restored.

What was searched

Initial pass: web search "telotristat ethyl hemoglobin anemia OR iron OR copper OR ferritin laboratory changes clinical trial" returned trial-protocol and review pages and no copper result; label keyword search for copper and zinc found nothing [1]. Repair pass (2026-10-07): keyword searches through summarizing fetches of the EU public assessment report [27] and the Canadian clinical review report [28] for copper, iron, vitamin and trace elements found nothing; TELEPATH [8], the pooled safety paper [9], the time-to-response paper [29] and the 14-patient single-arm trial [30] report no copper, ceruloplasmin or trace element values. Crossref bibliographic searches for TPH1 inhibition with iron or hemoglobin and for telotristat with iron, copper or anemia were rate limited (HTTP 429) and not retried. Further web searches were stopped by the tool's search limit. The Ananda abstract reports trace element deficiency 30.4% in GEP-NET patients without a telotristat link and without naming copper [15].

Channel outcomes

Label, EU report and Canadian review opened and searched; PubMed listing, Europe PMC REST and two Crossref queries blocked by 429; WebSearch budget exhausted before the final planned copper and iron queries. Genuine thin literature with a tooling-limited remainder.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence and no circulating claim of telotristat iron effects found. The anemia count cannot be reassigned to iron. Not a finding of safety.

What was searched

Same searches as Copper, plus label keyword search for iron, anemia, hemoglobin (none found) [1]. No ferritin, transferrin saturation, serum iron or iron absorption measurement in telotristat users was found in [8][9][27][28][29][30]. The pooled safety paper lists baseline anemia in 15% of 239 patients and TELEPATH lists anemia as an adverse event in 10.5% [8][9]; these are outcomes with no iron indices (Hard Rule 2) and are written up in the Oxygen delivery/utilization yellow entry, not here. A web search for TPH knockout or inhibitor hematology and hepcidin returned only generic hepcidin pages, and a further search for telotristat with ferritin was blocked by the search limit.

Channel outcomes

Same as Copper. Tooling-limited for database searches; clean zero on label, EU report and Canadian review.

Limits on what this shows

• Null findings: Minimal change in microbial abundance in neonatal rats [19]; no metabolic effect of the shifted microbiota on transfer [18]; the PNAS 2019 study [17] was re-read in a targeted pass and reported no microbiota sequencing for LP533401-alone groups.
• At-risk subgroups: Not defined. Competing GI factors in the indication population: diarrhea, somatostatin analog co-therapy, prior bowel surgery, and telotristat-related constipation.

Regulatory status

No microbiome statement in the label text [1][2]. Flatulence 7% vs 2% placebo and constipation are clinical events, not microbiome measures [1][8]. About 92.8% of a radiolabeled dose was recovered in feces [1], so luminal exposure is possible, but microbiome exposure was not measured (inference only).

Population evidence

Cohort test: telotristat was NOT in any cohort below. Ling et al. 2024 [19] (abstract read via Crossref and OpenAlex; full text not opened, sample size not captured): neonatal rats given LP533401 from day 4; at day 11 colon showed deeper crypts and thinner myenteric layers; metagenomics showed increased two-component signaling and tyrosine metabolism pathways "with minimal changes to microbial abundance"; metabolomics showed decreased ascorbate and elevated succinic acid. Martin et al. ANZOS 2017 abstract [26]: adult mice treated 28 days with antibiotics, LP533401 or both; "LP533401 treated mice showed a shift in Day 28 faecal microbiota composition compared to Day 0 and controls" (no taxa, effect sizes or n given). Martin et al. ANZOS 2021 abstract [18]: inhibition of gut serotonin synthesis "significantly altered the gut microbiome and microbial metabolite abundance after 28 days"; in recipient mice given that microbiota (D-FMT) the shift was not associated with changes in blood glucose, weight or duodenal 5-HT. Human data for telotristat: none found; the Mendelian randomization paper [16] tested no drug effect.

Mechanism

Plausible but unquantified (Tier C). Host serotonin synthesis and gut microbiota influence each other: germ-free mice show reduced colonic Tph1 expression [31], and antibiotic microbiota depletion acts partly through gut serotonin [17][26]. Whether peripheral TPH inhibition by telotristat in humans changes the microbiome is untested.

Counter-evidence held on record

Counter-evidence and confounding Direction is inconsistent between studies (functional change with minimal abundance change in rats, composition shift in mice), the compound, species, age and dose differ from telotristat in patients, and two of three sources are conference abstracts. No dysbiosis marker, diversity index or clinical microbiome outcome exists for telotristat users. Framing caution A class-extrapolation research flag, not a claim that telotristat disrupts the microbiome. No probiotic, prebiotic or dietary change is implied.

Limits on what this shows

• Null findings: TELESTAR and TELECAST time-to-response analysis (211 patients, telotristat 250 and 500 mg arms) [29] and a 14-patient single-arm dose-escalation trial [30] report no hemoglobin, anemia or nutritional laboratory data. The Canadian clinical review reported common adverse events (nausea, abdominal pain, ALT increased) without anemia [28]. Placebo-arm anemia rates from TELESTAR and TELECAST were not retrieved.
• At-risk subgroups: Patients with metastatic NETs, prior surgery or chemotherapy, bleeding, hepatic metastases or poor intake; defined by disease, not by drug.

Regulatory status

No hemoglobin, anemia or hematology statement in the US label text (keyword search through a summarizing fetch) [1][2]. A search of the EU public assessment report found no anaemia, haemoglobin or haematology statement; the only repeat-dose toxicology line noted was in dogs at 100 mg/kg/day or more (stool character changes, hypospermatogenesis) with no blood parameter change documented [27]. A search of the Canadian drug review clinical report found no anemia or hemoglobin content [28].

Population evidence

TELEPATH [8] (n=124, open-label extension, about 102.6 weeks mean, no comparator): anemia in 13 patients (10.5%), 19 events, under blood and lymphatic system disorders; no hemoglobin values or iron indices. Pooled safety analysis [9] (n=239): anemia in the baseline medical history of 36 patients (15%), and 126 patients (52.7%) had baseline conditions potentially due to carcinoid syndrome, including anemia, carcinoid heart disease or weight loss; hemoglobin and ferritin were not reported. Both are Tier A cohorts that include telotristat, but they cannot attribute anemia to the drug: one counts events with no comparator and the other counts history at entry (different measures that cannot be subtracted).

Mechanism

Absent in retrieved sources. No retrieved study shows that tryptophan hydroxylase inhibition changes erythropoiesis, hemoglobin synthesis or red-cell oxygen carriage. The mechanism route that would matter (iron or copper handling) is itself ungraded below.

Counter-evidence held on record

Counter-evidence and confounding Confounding by indication is presumed (Hard Rule 6): anemia is documented in 15% of the pooled cohort before treatment, and metastatic malignancy, bleeding and prior therapy are competing explanations. The 10.5% event rate and the 15% baseline history cannot be compared directly, so neither a protective nor a harmful effect can be inferred. Framing caution Not iron deficiency and not an oxygen-delivery deficit from this drug. Never imply iron supplementation; no dose appears in this dossier. Independent of ATP production (Hard Rule 7).

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C measurement of ATP synthesis or cellular ATP for telotristat or another TPH inhibitor, and no circulating "low energy" claim for telotristat. Kept independent of Mitochondrial burden and Oxygen delivery/utilization (Hard Rule 7). Not a finding of safety.

What was searched

Initial pass: web searches with respiration, ROS and oxidative terms; label keyword search for ATP found nothing [1]. The in vitro telotristat study [10] measured MTT metabolic activity (unchanged) but not ATP content or membrane potential. Repair pass: the EU public assessment report and Canadian review searches for ATP and energy metabolism found nothing [27][28]; a Crossref bibliographic search for telotristat with mitochondria, oxidative stress and ATP returned only generic mitochondrial literature with no telotristat record. The rodent TPH-inhibition study [25] measured whole-animal oxygen consumption and heat production (energy expenditure) and explicitly did not report ATP levels, so it supports the Mitochondrial burden entry, not this one. Fatigue was reported in 25.8% of TELEPATH patients (41 events) and in 29% at baseline in the pooled safety cohort [8][9]; TELEPATH links higher bowel movement frequency with more fatigue. Fatigue is a clinical outcome and a disease symptom, not an ATP measurement (Hard Rule 2).

Channel outcomes

Label, EU report, Canadian review and trial papers searched; PubMed listing and Europe PMC REST blocked; WebSearch budget exhausted. Tooling-limited plus thin literature.