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· 2 min read

Excited to share that our paper "Many Needles in a Haystack: Active Hit Discovery for Perturbation Experiments" has been accepted at ICML 2026 — see you in Seoul! 🇰🇷

CRISPR and single-cell perturbation screens can test thousands of genes, but budgets are tight and the genes that actually move a phenotype are rare and scattered. The hard question is no longer can we screen? — it's which perturbations should we run next?

We tackle this with a lab-in-the-loop design loop: an AI model proposes a batch of genes to perturb, the lab runs them, the readouts update the model, and the cycle repeats — each round getting smarter about where the hits are hiding.

The catch is that standard active-learning methods chase a single "best" gene, but biology rarely works that way: hits sit in multiple pathways and cellular contexts. Our method, Probability-of-Hit, instead asks the right question — which genes are most likely to cross the hit threshold? — and recovers more biologically meaningful hits across five real immunology screens (T-cell activation, NK cytotoxicity, tau, SARS-CoV-2).

The upshot for experimentalists: more hits per plate, fewer wasted wells.

Figure: UMAP of gene embeddings and closed-loop experimental design for active hit discovery

Congratulations to first authors Andrea Rubbi and Arpit Merchant, postdoc Sam Ogden, Amir Hossein Hosseini Akbarnejad, and thanks to Pietro Liò and Sattar Vakili for the great collaboration.

· One min read

Mixture-of-Experts (MoE) is a powerful way to scale large language models (LLMs): instead of running the full model for every token, a router activates only a few "experts," giving more capacity at roughly the same compute.

But routing is still a sore spot. Most MoE systems use Top-k + Softmax, where expert selection is discrete—so you don't get clean end-to-end gradients. In practice, this can lead to unstable routing, calibration issues, and uneven expert usage.

In our ICLR 2026 paper, we introduce DirMoE — a fully differentiable probabilistic router that separates which experts fire (Bernoulli) from how their weights are assigned (Dirichlet). We also add a simple "sparsity knob" (Simpson-index penalty) to control the expected number of active experts, without relying on load-balancing losses that can homogenize experts.

Results: DirMoE matches or exceeds vanilla MoE throughput (no extra bottlenecks), is strong/competitive on zero-shot benchmarks (ARC, BoolQ, PIQA, …), and leads to clearer expert specialization (interpretable domain focus like ArXiv/Books/GitHub code).

DirMoE: Dirichlet-Routed Mixture of Experts — disentangling expert selection (Bernoulli) from expert contribution (Dirichlet)

Led by Hesam Asadollahzadeh and Amirhossein Vahidi.

Read the paper on OpenReview · Thread on X

· One min read

I am excited that our work from my time at Meta AI and collaboration with Helmholtz Munich on modeling single-cell perturbations (e.g., drugs, disease, CRISPR manipulations) is now featured on the cover of Molecular systems biology. Thanks to all collaborators and my co-authors for making this happen.

MDSI award.

About the paper:

Lotfollahi, M+., Klimovskaia Susmelj+, A., De Donno, C+., Hetzel, L., Ji, Y., Ibarra, I. L., ... & Theis, F. J.

[Molecular Systems Biology (2023)], [code], [Facebook AI blogpost], [state of AI report 2021], [featured cover].