Exploring Polymorphism: Hydrochloride Salts of Pitolisant and Analogues
Bibliographic record
Abstract
Pitolisant hydrochloride is used to treat excessive daytime sleepiness in adults with narcolepsy. The drug is formulated as a crystalline solid, and a monoclinic P 2 1 form has been claimed in patents, but little additional information about the structure and polymorphism of the compound has been published. No new forms were obtained when we grew crystals from solution under various conditions. Re-examination of the crystals revealed a disordered and partially hydrated structure that resembles the one reported earlier but is not identical. Further insight was obtained by synthesizing analogues of pitolisant with its Cl substituent replaced by Me, F, and Br, followed by structural analysis of the hydrochloride salts by X-ray diffraction. Pitolisant hydrochloride and its three analogues showed very similar solid-state behavior, and each compound yielded new metastable forms when crystallized from melts. The lifetime of metastable form III of pitolisant hydrochloride could be extended significantly by adding small amounts of the fluoro analogue, but none of the metastable forms could be obtained as single crystals suitable for structural analysis. Computational predictions of the polymorphic landscapes of pitolisant hydrochloride and its analogues identified possible structures of the metastable forms. Dual experimental and computational approaches are already widely used in polymorphic screening, but our work shows the value of broadening these searches to include sets of structural analogues.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".